Urinary tract infections — MCQs

10 questions

A 62-year-old man comes to the physician because of a 2-day history of fever, chills, and flank pain. Five days ago, he was catheterized for acute urinary retention. His temperature is 39.3°C (102.7°F). Physical examination shows right-sided costovertebral angle tenderness. Urine studies show numerous bacteria and WBC casts. Urine culture on blood agar grows mucoid, gray-white colonies. Urine culture on eosin methylene blue agar grows purple colonies with no metallic green sheen. Which of the following is the most likely causal pathogen?

A 62-year-old woman with type 2 diabetes mellitus is brought to the emergency room because of a 3-day history of fever and shaking chills. Her temperature is 39.4°C (103°F). Examination of the back shows right costovertebral angle tenderness. Analysis of the urine shows WBCs, WBC casts, and gram-negative rods. Ultrasound examination of the kidneys shows no signs of obstruction. Biopsy of the patient's kidney is most likely to show which of the following?

A 76-year-old woman presents to the primary care physician for a regular check-up. History reveals that she has had episodes of mild urinary incontinence over the past 2 years precipitated by sneezing or laughing. However, over the past week, her urinary incontinence has occurred during regular activities. Her blood pressure is 140/90 mm Hg, heart rate is 86/min, respiratory rate is 22/min, and temperature is 37.7°C (99.9°F). Physical examination is remarkable for suprapubic tenderness. Urinalysis reveals 15 WBCs/HPF, positive nitrites, and positive leukocyte esterase. Which of the following is the best next step for this patient?

A 26-year-old female presents to her primary care physician concerned that she has contracted a sexually transmitted disease. She states that she is having severe pain whenever she urinates and seems to be urinating more frequently than normal. She reports that her symptoms started after she began having unprotected sexual intercourse with 1 partner earlier this week. The physician obtains a urinalysis which demonstrates the following, SG: 1.010, Leukocyte esterase: Positive, Nitrites: Positive, Protein: Trace, pH: 5.0, RBC: Negative. A urease test is performed which is negative. This patient has most likely been infected with which of the following organisms?

A 33-year-old female presents with recent onset of painful urination, fever, and right flank pain. Urinary sediment analysis is positive for the presence of white blood cell casts and Gram-negative bacteria. She has not recently started any new medications. What is the most likely diagnosis in this patient?

A 25-year-old woman comes to the physician because of a 2-day history of a burning sensation when urinating and increased urinary frequency. She is concerned about having contracted a sexually transmitted disease. Physical examination shows suprapubic tenderness. Urinalysis shows a negative nitrite test and positive leukocyte esterases. Urine culture grows organisms that show resistance to novobiocin on susceptibility testing. Which of the following is the most likely causal organism of this patient's symptoms?

A 22-month-old girl is brought to the emergency department with a 24-hour history of fever, irritability, and poor feeding. The patient never experienced such an episode in the past. She met the normal developmental milestones, and her vaccination history is up-to-date. She takes no medications, currently. Her temperature is 38.9°C (102.0°F). An abdominal examination reveals general tenderness without organomegaly. The remainder of the physical examination shows no abnormalities. Laboratory studies show the following results: Urine Blood 1+ WBC 10–15/hpf Bacteria Many Nitrite Positive Urine culture from a midstream collection reveals 100,000 CFU/mL of Escherichia coli. Which of the following interventions is the most appropriate next step in evaluation?

A 23-year-old woman gravida 2, para 1 at 12 weeks' gestation comes to the physician for her initial prenatal visit. She feels well. She was treated for genital herpes one year ago and gonorrhea 3 months ago. Medications include folic acid and a multivitamin. Vital signs are within normal limits. Pelvic examination shows a uterus consistent in size with a 12-week gestation. Urine dipstick is positive for leukocyte esterase and nitrite. Urine culture shows E. coli (> 100,000 colony forming units/mL). Which of the following is the most appropriate next step in management?

A 48-year-old man comes to the emergency department because of a 2-hour history of severe left-sided colicky flank pain that radiates towards his groin. He has vomited twice. Last year, he was treated with ibuprofen for swelling and pain of his left toe. He drinks 4-5 beers most days of the week. Examination shows left costovertebral angle tenderness. An upright x-ray of the abdomen shows no abnormalities. A CT scan of the abdomen and pelvis shows an 9-mm stone in the proximal ureter on the left. Which of the following is most likely to be seen on urinalysis?

Q10

A newborn girl is rushed to the neonatal ICU after an emergency cesarean section due to unstable vital signs after delivery. The pregnancy was complicated due to oligohydramnios and pulmonary hypoplasia. Gestation was at 38 weeks. APGAR scores were 6 and 8 at 1 and 5 minutes respectively. The newborn’s temperature is 37.0°C (98.6°F), the blood pressure is 60/40 mm Hg, the respiratory rate is 45/min, and the pulse is 140/min. Physical examination reveals irregularly contoured bilateral abdominal masses. Abdominal ultrasound reveals markedly enlarged echogenic kidneys (5 cm in the vertical dimension) with multiple cysts in the cortex and medulla. This patient is at highest risk of which of the following complications?

Urinary tract infections US Medical PG Practice Questions and MCQs

Question 1: A 62-year-old man comes to the physician because of a 2-day history of fever, chills, and flank pain. Five days ago, he was catheterized for acute urinary retention. His temperature is 39.3°C (102.7°F). Physical examination shows right-sided costovertebral angle tenderness. Urine studies show numerous bacteria and WBC casts. Urine culture on blood agar grows mucoid, gray-white colonies. Urine culture on eosin methylene blue agar grows purple colonies with no metallic green sheen. Which of the following is the most likely causal pathogen?

A. Escherichia coli
B. Klebsiella pneumoniae (Correct Answer)
C. Pseudomonas aeruginosa
D. Proteus mirabilis
E. Staphylococcus saprophyticus

Explanation: ***Klebsiella pneumoniae*** - The presence of **mucoid, gray-white colonies** on blood agar and **purple colonies with no metallic green sheen** on EMB agar, along with a history of catheterization, fever, and flank pain strongly suggests *Klebsiella pneumoniae*. - *Klebsiella* is a common cause of **catheter-associated UTIs** and often produces mucoid colonies due to its capsule. *Escherichia coli* - *E. coli* typically produces **metallic green sheen** on EMB agar due to rapid lactose fermentation, which is absent in this case. - While *E. coli* is a common cause of UTIs, the specific culture findings differentiate it from *Klebsiella*. *Pseudomonas aeruginosa* - *Pseudomonas* often produces a **grape-like odor** and distinctive **blue-green pigment** on agar, neither of which is mentioned. - It does not ferment lactose and would thus not produce purple colonies on EMB, but rather appear as colorless or clear colonies. *Proteus mirabilis* - *Proteus mirabilis* is known for its **swarming motility** on agar, which creates a characteristic spreading growth pattern, not merely mucoid colonies. - It also produces **urease**, which can lead to alkaline urine and struvite stones, but the distinguishing colony morphology is not met. *Staphylococcus saprophyticus* - *Staphylococcus saprophyticus* is a **Gram-positive coccus** and would not grow purple colonies on EMB agar, which is selective for Gram-negative bacteria. - It is a common cause of UTIs in young, sexually active women, which does not fit the patient's demographic.

Question 2: A 62-year-old woman with type 2 diabetes mellitus is brought to the emergency room because of a 3-day history of fever and shaking chills. Her temperature is 39.4°C (103°F). Examination of the back shows right costovertebral angle tenderness. Analysis of the urine shows WBCs, WBC casts, and gram-negative rods. Ultrasound examination of the kidneys shows no signs of obstruction. Biopsy of the patient's kidney is most likely to show which of the following?

A. Polygonal clear cells filled with lipids and carbohydrates
B. Polymorphonuclear leukocytes in tubules (Correct Answer)
C. Tubular eosinophilic casts
D. Widespread granulomatous tissue and foamy macrophages
E. Cystic dilation of the renal medulla

Explanation: ***Polymorphonuclear leukocytes in tubules*** - The patient presents with classic signs and symptoms of **acute pyelonephritis**, including fever, chills, **costovertebral angle tenderness**, **WBCs and WBC casts** in the urine, and **gram-negative rods**, indicating a bacterial infection of the kidney parenchyma. - A kidney biopsy in acute pyelonephritis would reveal an intense **inflammatory infiltrate** primarily composed of **polymorphonuclear leukocytes (neutrophils)** within the renal tubules and interstitium, responding to the bacterial invasion. *Polygonal clear cells filled with lipids and carbohydrates* - This description is characteristic of **renal cell carcinoma**, specifically the **clear cell subtype**. - While this is a possible renal pathology, it does not align with the acute infectious presentation of fever, chills, CVA tenderness, and urinary findings of infection. *Tubular eosinophilic casts* - **Eosinophilic casts** in renal tubules are typical of **acute tubular necrosis (ATN)**, often resulting from ischemic or nephrotoxic injury. - Although ATN can cause acute renal failure, the presence of **fever, shaking chills, and gram-negative rods** points more directly to an active bacterial infection. *Widespread granulomatous tissue and foamy macrophages* - This finding is suggestive of a granulomatous disease like **tuberculosis** or **xanthogranulomatous pyelonephritis**. - While **xanthogranulomatous pyelonephritis** is a severe chronic form of pyelonephritis, it typically involves a destructive mass and often presents with a more subacute or chronic course rather than acute onset with shaking chills and evidence of uncomplicated bacterial infection. *Cystic dilation of the renal medulla* - This points to conditions such as **medullary sponge kidney** or **polycystic kidney disease**. - These are primarily congenital or developmental anomalies and do not explain the acute signs of infection and inflammation seen in this patient.

Question 3: A 76-year-old woman presents to the primary care physician for a regular check-up. History reveals that she has had episodes of mild urinary incontinence over the past 2 years precipitated by sneezing or laughing. However, over the past week, her urinary incontinence has occurred during regular activities. Her blood pressure is 140/90 mm Hg, heart rate is 86/min, respiratory rate is 22/min, and temperature is 37.7°C (99.9°F). Physical examination is remarkable for suprapubic tenderness. Urinalysis reveals 15 WBCs/HPF, positive nitrites, and positive leukocyte esterase. Which of the following is the best next step for this patient?

A. Pelvic floor muscle training
B. Ultrasound scan of the kidneys, urinary tract, and bladder
C. Cystoscopy
D. Urine culture (Correct Answer)
E. Start empirical antibiotic therapy

Explanation: ***Urine culture*** - The patient presents with classic **signs of a urinary tract infection (UTI)**: new onset urinary incontinence worsening, suprapubic tenderness, and urinalysis positive for **WBCs, nitrites, and leukocyte esterase**. - A urine culture is essential to **confirm the diagnosis of UTI**, identify the causative organism, and determine antibiotic sensitivity before initiating targeted treatment. *Pelvic floor muscle training* - This intervention is appropriate for **stress urinary incontinence (SUI)**, which the patient initially experienced, but it will not address the acute infection. - While it may be considered after UTI treatment for managing chronic incontinence, it's NOT the immediate priority given the acute infectious symptoms. *Ultrasound scan of the kidneys, urinary tract, and bladder* - An ultrasound might be considered if there were concerns for **obstruction**, **pyelonephritis**, or recurrent UTIs after treatment, but it is not the immediate diagnostic step for an acute, uncomplicated UTI. - The primary goal is to identify and treat the infection first. *Cystoscopy* - **Cystoscopy** is an invasive procedure generally reserved for investigating causes of recurrent UTIs, hematuria, or bladder abnormalities after initial treatment failures or in specific clinical scenarios, not for initial diagnosis of an apparent UTI. - It would be premature and unnecessary at this stage without ruling out a simple infection. *Start empirical antibiotic therapy* - While antibiotics are indeed needed, starting empirical therapy without a culture could lead to **antibiotic resistance** or ineffective treatment if the causative organism is not susceptible to the chosen antibiotic. - Given the suprapubic tenderness and urinalysis findings, a UTI is highly likely, but **culture and sensitivity guided therapy** is the best practice for optimal patient outcomes and to prevent resistance, especially in an elderly patient.

Question 4: A 26-year-old female presents to her primary care physician concerned that she has contracted a sexually transmitted disease. She states that she is having severe pain whenever she urinates and seems to be urinating more frequently than normal. She reports that her symptoms started after she began having unprotected sexual intercourse with 1 partner earlier this week. The physician obtains a urinalysis which demonstrates the following, SG: 1.010, Leukocyte esterase: Positive, Nitrites: Positive, Protein: Trace, pH: 5.0, RBC: Negative. A urease test is performed which is negative. This patient has most likely been infected with which of the following organisms?

A. Enterobacter cloacae
B. Staphylococcus saprophyticus
C. Proteus mirabilis
D. Klebsiella pneumoniae
E. Escherichia coli (Correct Answer)

Explanation: ***Escherichia coli*** - The urinalysis findings of **positive leukocyte esterase**, **nitrites**, and **trace protein** with a slightly acidic pH (5.0) are highly suggestive of a **urinary tract infection (UTI)**. - *E. coli* is the most common cause of UTIs, especially in young, sexually active women, and is typically **urease-negative**, consistent with the information provided. - *E. coli* accounts for **80-90% of uncomplicated UTIs** and produces nitrites from dietary nitrates, making it the most likely pathogen in this clinical scenario. *Enterobacter cloacae* - While *Enterobacter cloacae* can cause UTIs, it is less common than *E. coli* in uncomplicated cases and is often associated with nosocomial infections or those in immunocompromised individuals. - Its urease activity can vary, so a negative urease test doesn't rule it out completely but makes *E. coli* a more likely primary choice in this context. *Staphylococcus saprophyticus* - *S. saprophyticus* is a common cause of UTIs in young, sexually active women (second most common cause after *E. coli*) and is typically **urease-negative**, which is consistent with the negative test. - However, the presence of **positive nitrites** points more strongly towards **Gram-negative bacteria** like *E. coli*, as *S. saprophyticus* is a **Gram-positive coccus** that does not produce nitrite reductase and therefore does not convert nitrates to nitrites. *Proteus mirabilis* - *Proteus mirabilis* is known for causing UTIs and is characteristically **urease-positive**, leading to alkaline urine (higher pH) and sometimes **struvite stones**. - The **negative urease test** and acidic urine pH (5.0) in this case effectively rule out *Proteus mirabilis*. *Klebsiella pneumoniae* - *Klebsiella pneumoniae* can cause UTIs and is generally **urease-negative**, but it is less frequently the cause of uncomplicated UTIs compared to *E. coli*. - Although it can produce nitrites, *E. coli* remains the most common etiology in this clinical scenario.

Question 5: A 33-year-old female presents with recent onset of painful urination, fever, and right flank pain. Urinary sediment analysis is positive for the presence of white blood cell casts and Gram-negative bacteria. She has not recently started any new medications. What is the most likely diagnosis in this patient?

A. Appendicitis
B. Cystitis
C. Pyelonephritis (Correct Answer)
D. Acute Interstitial Nephritis
E. Pelvic Inflammatory Disease

Explanation: ***Pyelonephritis*** - The combination of **painful urination**, **fever**, **right flank pain**, and **white blood cell casts** in the urine is highly indicative of pyelonephritis, an infection of the renal parenchyma. - **White blood cell casts** are pathognomonic for inflammation within the renal tubules and are a key differentiating feature that points to an upper urinary tract infection. *Appendicitis* - While appendicitis can cause **right-sided abdominal pain** and **fever**, it typically does not present with painful urination or urinary sediment abnormalities like white blood cell casts. - The pain is usually localized to the **right lower quadrant** and often migrates, which is not characteristic of flank pain. *Cystitis* - Cystitis involves bladder inflammation and causes **painful urination**, **frequency**, and **urgency**, but typically does not cause **fever** or **flank pain**, and **white blood cell casts** are absent. - It is an infection limited to the **lower urinary tract**, without renal parenchymal involvement. *Acute Interstitial Nephritis* - This condition is often associated with a **drug hypersensitivity reaction**, causing inflammation in the renal interstitium, but typically presents with **eosinophilia**, rash, and renal failure, not usually with white blood cell casts directly from infection. - While it can cause renal dysfunction and sometimes fever, the presence of **Gram-negative bacteria** and **WBC casts** strongly points to an infection rather than an allergic reaction. *Pelvic Inflammatory Disease* - PID causes **lower abdominal pain**, **fever**, and sometimes painful urination if there's concurrent urethritis, but it is not associated with **flank pain** or **white blood cell casts** in the urine. - It is an infection of the **female reproductive organs**, often caused by sexually transmitted organisms, and would typically present with cervical motion tenderness.

Question 6: A 25-year-old woman comes to the physician because of a 2-day history of a burning sensation when urinating and increased urinary frequency. She is concerned about having contracted a sexually transmitted disease. Physical examination shows suprapubic tenderness. Urinalysis shows a negative nitrite test and positive leukocyte esterases. Urine culture grows organisms that show resistance to novobiocin on susceptibility testing. Which of the following is the most likely causal organism of this patient's symptoms?

A. Klebsiella pneumoniae
B. Proteus mirabilis
C. Pseudomonas aeruginosa
D. Staphylococcus epidermidis
E. Staphylococcus saprophyticus (Correct Answer)

Explanation: ***Staphylococcus saprophyticus*** - This organism is the **second most common cause of UTIs in young, sexually active women** (after *E. coli*), making it highly consistent with the patient's demographics and presentation. - *S. saprophyticus* is characterized by **resistance to novobiocin**, which is the key laboratory test differentiating it from *S. epidermidis* (novobiocin-sensitive). - It is **nitrite-negative** as it does not reduce nitrates to nitrites, consistent with the negative nitrite test. *Klebsiella pneumoniae* - While *K. pneumoniae* can cause UTIs, it is typically **nitrite-positive** because it reduces nitrates to nitrites, which contradicts the negative nitrite test result. - This gram-negative organism would not be tested for novobiocin susceptibility, as this antibiotic is used specifically to differentiate staphylococcal species. *Proteus mirabilis* - *P. mirabilis* is known for causing UTIs and is **nitrite-positive** due to its ability to reduce nitrates, which is inconsistent with the patient's negative nitrite test. - It also produces **urease**, leading to alkaline urine and struvite stones, which are not features of this acute presentation. *Pseudomonas aeruginosa* - *P. aeruginosa* is **nitrite-negative** (it does not reduce nitrates), which matches the test result. - However, it is typically associated with **hospital-acquired UTIs**, catheter-related infections, or infections in immunocompromised patients, not uncomplicated community-acquired UTIs in healthy young women. - Novobiocin testing is not routinely used for gram-negative organisms. *Staphylococcus epidermidis* - *S. epidermidis* is a common **skin commensal** and frequent contaminant in urine cultures. - Critically, it is **novobiocin-sensitive**, which distinguishes it from *S. saprophyticus* and makes it incompatible with the culture findings. - It rarely causes true UTIs unless associated with indwelling catheters or prosthetic devices.

Question 7: A 22-month-old girl is brought to the emergency department with a 24-hour history of fever, irritability, and poor feeding. The patient never experienced such an episode in the past. She met the normal developmental milestones, and her vaccination history is up-to-date. She takes no medications, currently. Her temperature is 38.9°C (102.0°F). An abdominal examination reveals general tenderness without organomegaly. The remainder of the physical examination shows no abnormalities. Laboratory studies show the following results: Urine Blood 1+ WBC 10–15/hpf Bacteria Many Nitrite Positive Urine culture from a midstream collection reveals 100,000 CFU/mL of Escherichia coli. Which of the following interventions is the most appropriate next step in evaluation?

A. No further testing
B. Voiding cystourethrography
C. Renal and bladder ultrasonography (Correct Answer)
D. Intravenous pyelography
E. Dimercaptosuccinic acid renal scan

Explanation: ***Renal and bladder ultrasonography*** - For a febrile infant or young child (2 to 24 months) with a first **culture-proven urinary tract infection (UTI)**, renal and bladder ultrasonography is the recommended imaging study. - This imaging is crucial to evaluate for **anatomic abnormalities** of the kidneys and urinary tract that could predispose to recurrent infections or renal damage. - Current AAP guidelines recommend ultrasound as the **initial imaging modality** to assess for conditions like vesicoureteral reflux (VUR), hydronephrosis, or obstructive uropathy. *No further testing* - This option is incorrect because a **febrile UTI** in a young child warrants imaging to rule out **underlying genitourinary abnormalities** that could predispose to recurrent infections or renal damage. - Skipping further evaluation could miss conditions like **vesicoureteral reflux (VUR)** or obstructive uropathy. *Voiding cystourethrography* - **Voiding cystourethrography (VCUG)** was historically recommended for all young children after a first UTI but is now reserved for specific situations, such as **abnormal renal/bladder ultrasound findings** or recurrent UTIs. - VCUG involves radiation exposure and catheterization, making it less favorable as a first-line imaging study. *Intravenous pyelography* - **Intravenous pyelography (IVP)** involves intravenous contrast and radiation, making it an **invasive and high-radiation study** that has largely been replaced by ultrasound and CT for evaluating the urinary tract. - It is not recommended as the initial imaging of choice for a child with a first UTI due to its **risks and availability of safer alternatives**. *Dimercaptosuccinic acid renal scan* - A **dimercaptosuccinic acid (DMSA) renal scan** is primarily used to detect **renal scarring** and assesses differential renal function. - While it can be useful in identifying long-term consequences of UTIs, it is not the primary imaging study for initial evaluation of **ureteral or bladder abnormalities** in a first febrile UTI.

Question 8: A 23-year-old woman gravida 2, para 1 at 12 weeks' gestation comes to the physician for her initial prenatal visit. She feels well. She was treated for genital herpes one year ago and gonorrhea 3 months ago. Medications include folic acid and a multivitamin. Vital signs are within normal limits. Pelvic examination shows a uterus consistent in size with a 12-week gestation. Urine dipstick is positive for leukocyte esterase and nitrite. Urine culture shows E. coli (> 100,000 colony forming units/mL). Which of the following is the most appropriate next step in management?

A. Perform cystoscopy
B. Administer gentamicin
C. Administer trimethoprim/sulfamethoxazole (TMP/SMX)
D. Administer amoxicillin/clavulanate (Correct Answer)
E. Perform renal ultrasound

Explanation: ***Administer amoxicillin/clavulanate*** - The patient has **asymptomatic bacteriuria** based on a positive urine dipstick for leukocyte esterase and nitrite and a urine culture showing *E. coli* (> 100,000 CFU/mL) in a pregnant patient. - **Amoxicillin/clavulanate** is a safe and effective first-line antibiotic for treating asymptomatic bacteriuria in pregnancy due to its broad spectrum and safety profile for the fetus. *Perform cystoscopy* - **Cystoscopy** is an invasive procedure typically reserved for evaluating persistent hematuria, recurrent UTIs despite appropriate therapy, or suspected bladder pathology. - It is not indicated for initial management of asymptomatic bacteriuria, especially in pregnancy, as it carries risks and offers no immediate therapeutic benefit for this condition. *Administer gentamicin* - **Gentamicin** is an aminoglycoside antibiotic that is generally **contraindicated in pregnancy** due to potential **fetal ototoxicity** and nephrotoxicity. - While effective against *E. coli*, its risks outweigh the benefits for asymptomatic bacteriuria, especially when safer alternatives are available. *Administer trimethoprim/sulfamethoxazole (TMP/SMX)* - **Trimethoprim/sulfamethoxazole (TMP/SMX)** is generally **avoided in the first trimester** of pregnancy due to concerns about **folate antagonism** (trimethoprim) and potential teratogenic effects, such as neural tube defects, particularly between 6-12 weeks' gestation. - The patient is at 12 weeks' gestation, making TMP/SMX a less safe choice compared to other antibiotics. *Perform renal ultrasound* - A **renal ultrasound** is typically performed if there are complications such as **pyelonephritis**, recurrent urinary tract infections, or suspicion of **structural abnormalities** in the urinary tract. - For asymptomatic bacteriuria, an ultrasound is not part of the initial management unless there are specific indications or if the infection does not resolve with appropriate antibiotic therapy.

Question 9: A 48-year-old man comes to the emergency department because of a 2-hour history of severe left-sided colicky flank pain that radiates towards his groin. He has vomited twice. Last year, he was treated with ibuprofen for swelling and pain of his left toe. He drinks 4-5 beers most days of the week. Examination shows left costovertebral angle tenderness. An upright x-ray of the abdomen shows no abnormalities. A CT scan of the abdomen and pelvis shows an 9-mm stone in the proximal ureter on the left. Which of the following is most likely to be seen on urinalysis?

A. Rhomboid-shaped crystals
B. Coffin-lid-like crystals
C. Red blood cell casts
D. Wedge-shaped crystals (Correct Answer)
E. Hexagon-shaped crystals

Explanation: ***Wedge-shaped crystals*** - The patient's history of **left toe swelling and pain** (suggestive of **gout**) and **alcohol consumption** strongly indicate **hyperuricemia** and predisposition to **uric acid stone** formation. - **Uric acid stones are radiolucent**, which explains why the **X-ray showed no abnormalities** despite a 9-mm stone being visible on CT scan—this is a classic presentation. - **Uric acid crystals** appear as **wedge-shaped, rhomboid, or pleomorphic** yellow-brown crystals in **acidic urine** (pH <5.5). - This is the most likely finding on urinalysis given the clinical context. *Rhomboid-shaped crystals* - **Rhomboid-shaped crystals** are also characteristic of **uric acid**, making this another acceptable description of the same crystal type. - Both "wedge-shaped" and "rhomboid" refer to **uric acid crystals**; however, "wedge-shaped" is the more commonly used descriptor in clinical practice. - If this were an option and wedge-shaped were not available, it would also be correct, but wedge-shaped is the better answer when both are present. *Coffin-lid-like crystals* - **Coffin-lid crystals** are characteristic of **struvite stones** (magnesium ammonium phosphate), which form in **alkaline urine** (pH >7) and are associated with **urease-producing bacteria** (e.g., Proteus, Klebsiella). - Struvite stones are **radiopaque** and would be visible on X-ray, which contradicts this presentation. - The patient has no signs of urinary tract infection. *Red blood cell casts* - **RBC casts** indicate **glomerular bleeding** and are seen in conditions like **glomerulonephritis**, not obstructive uropathy from stones. - While **hematuria** (RBCs in urine) is common with nephrolithiasis, **RBC casts** are not typical and would suggest primary renal parenchymal disease. *Hexagon-shaped crystals* - **Hexagonal crystals** are pathognomonic for **cystine stones**, which occur in **cystinuria**, a rare autosomal recessive disorder of amino acid transport. - Cystine stones are **weakly radiopaque** and would show faint opacity on X-ray. - This condition typically presents in childhood or young adulthood, not at age 48, and has no association with gout.

Question 10: A newborn girl is rushed to the neonatal ICU after an emergency cesarean section due to unstable vital signs after delivery. The pregnancy was complicated due to oligohydramnios and pulmonary hypoplasia. Gestation was at 38 weeks. APGAR scores were 6 and 8 at 1 and 5 minutes respectively. The newborn’s temperature is 37.0°C (98.6°F), the blood pressure is 60/40 mm Hg, the respiratory rate is 45/min, and the pulse is 140/min. Physical examination reveals irregularly contoured bilateral abdominal masses. Abdominal ultrasound reveals markedly enlarged echogenic kidneys (5 cm in the vertical dimension) with multiple cysts in the cortex and medulla. This patient is at highest risk of which of the following complications?

A. Portal hypertension (Correct Answer)
B. Subarachnoid hemorrhage
C. Acute renal failure
D. Recurrent UTI
E. Emphysema

Explanation: ***Portal hypertension*** * The presentation of **oligohydramnios**, **pulmonary hypoplasia**, and **enlarged, echogenic kidneys with multiple cysts** in a newborn is consistent with **autosomal recessive polycystic kidney disease (ARPKD)**. * ARPKD is invariably associated with **congenital hepatic fibrosis**, which leads to **portal hypertension** due to periportal fibrosis and obstruction of intrahepatic portal blood flow. This is the hallmark extra-renal complication of ARPKD. *Subarachnoid hemorrhage* * Subarachnoid hemorrhage from berry aneurysm rupture is associated with **autosomal dominant polycystic kidney disease (ADPKD)**, not ARPKD. * There are no specific clinical features or imaging findings in this case that would suggest intracranial hemorrhage as the highest risk complication. *Acute renal failure* * While neonates with ARPKD can develop renal insufficiency and progressive chronic kidney disease, the question asks for the "highest risk **complication**" rather than the primary disease manifestation. * **Portal hypertension from congenital hepatic fibrosis** is the most significant distinct complication that develops as a consequence of ARPKD, often manifesting in childhood with hepatosplenomegaly, esophageal varices, and hypersplenism. *Recurrent UTI* * Recurrent UTIs require structural abnormalities like vesicoureteral reflux or urinary stasis, which are not primary features of ARPKD. * While children with kidney disease may have increased infection risk, recurrent UTIs are not a direct or characteristic complication of the cystic kidney disease in ARPKD. *Emphysema* * **Pulmonary hypoplasia** (underdeveloped lungs from oligohydramnios/Potter sequence) is present in this case, but this is not the same as emphysema. * Emphysema involves destruction of alveolar walls and is typically seen in adults with chronic obstructive pulmonary disease or alpha-1 antitrypsin deficiency, not in neonates with pulmonary hypoplasia.

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