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?

Ultrasound scan of the kidneys, urinary tract, and bladder

Start empirical antibiotic therapy

A 28-year-old woman presents to the emergency department with fever, chills, nausea, vomiting, and right flank pain for 2 days. Temperature is 39.2°C (102.6°F), blood pressure is 95/60 mmHg, pulse is 110/min, and respirations are 18/min. She appears ill and is unable to tolerate oral fluids. Physical examination shows right costovertebral angle tenderness. Urinalysis shows: Protein 1+ Leukocyte esterase positive Nitrite positive RBC 2/hpf WBC 90/hpf WBC casts numerous Which of the following is the most appropriate next step in management?

Admit the patient and treat with intravenous levofloxacin

Treat on an outpatient basis with ciprofloxacin

Wait for culture results and treat accordingly

Treat on an outpatient basis with nitrofurantoin

Admit the patient and perform a CT scan of the abdomen

A 1-year-old boy is brought to the physician because of irritability and poor feeding that began 2 days ago. His mother reports that he has been crying more than usual during this period. He refused to eat his breakfast that morning and has not taken in any food or water since that time. He has not vomited. When changing the boy's diapers this morning, the mother noticed his urine had a strong smell and pink color. He has not passed urine since then. He was born at term and has been healthy. He appears ill. His temperature is 36.8°C (98.2°F), pulse is 116/min, and blood pressure is 98/54 mm Hg. The boy cries when the lower abdomen is palpated. Which of the following is the most appropriate next step in management?

Perform transurethral catheterization

Obtain clean catch urine sample

Perform voiding cystourethrogram

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?

Renal and bladder ultrasonography

Dimercaptosuccinic acid renal scan

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?

Administer amoxicillin/clavulanate

Administer trimethoprim/sulfamethoxazole (TMP/SMX)

A 13-month-old female infant is brought to the pediatrician by her stepfather for irritability. He states that his daughter was crying through the night last night, but she didn’t want to eat and was inconsolable. This morning, she felt warm. The father also notes that she had dark, strong smelling urine on the last diaper change. The patient’s temperature is 101°F (38.3°C), blood pressure is 100/72 mmHg, pulse is 128/min, and respirations are 31/min with an oxygen saturation of 98% on room air. A urinalysis is obtained by catheterization, with results shown below: Urine: Protein: Negative Glucose: Negative White blood cell (WBC) count: 25/hpf Bacteria: Many Leukocyte esterase: Positive Nitrites: Positive In addition to antibiotics, which of the following should be part of the management of this patient’s condition?

Repeat urine culture in 3 weeks

Urinary tract infections in children for USMLE Step 1: High-Yield Pediatrics Lessons

Etiology & Risks - The Usual Suspects

Primary Culprit: Uropathogenic E. coli (UPEC) causes >85% of cases.
Other Pathogens: Klebsiella, Proteus (↑ urine pH, stones), Enterococcus, S. saprophyticus (adolescent girls).
Key Risk Factors:
- Anatomic: Vesicoureteral Reflux (VUR), Posterior Urethral Valves (PUV), phimosis in uncircumcised boys <1 yr.
- Functional: Bladder & Bowel Dysfunction (BBD), constipation.

⭐ In children with recurrent febrile UTIs, the prevalence of Vesicoureteral Reflux (VUR) can be as high as 30-40%.

Vesicoureteral Reflux (VUR) Grading Diagram

Clinical Clues - Age is Key

Neonates (<1 mo): Non-specific signs rule. Presents like sepsis: fever/hypothermia, jaundice, poor feeding, lethargy.
Infants (1-24 mo): Fever is often the only sign. Suspect with irritability, vomiting, poor weight gain.
Toddlers/Preschool (2-5 yrs): More specific symptoms appear. Abdominal pain, dysuria, frequency, foul-smelling urine.
School-Aged (>5 yrs): Classic adult-like picture. Dysuria, frequency, urgency, suprapubic pain. Flank pain suggests pyelonephritis.

⭐ In children < 2 years, any fever without a clear source warrants a urine examination to rule out UTI.

Diagnosis - Confirm the Culprit

Urine Sample Collection: Method depends on age & toilet-training status.
- Gold Standard (Most sterile): Suprapubic Aspiration (SPA).
- Best practical method: Urethral Catheterization.
- Toilet-trained children: Mid-stream clean-catch urine (MSU).
- Screening ONLY: Urine bag. High contamination rate; a negative result is useful, but a positive result requires confirmation with a better sample.
Urinalysis:
- Dipstick: Positive Leukocyte Esterase (LE) for pyuria & Nitrites for Enterobacteriaceae.
- Microscopy: Pyuria (>5 WBCs/hpf) & Bacteriuria.

⭐ A combination of positive Leukocyte Esterase AND Nitrites on dipstick is highly suggestive of UTI.

Urine Culture & Sensitivity: Gold standard for diagnosis.

Management & Imaging - The Action Plan

Initial Management (Empiric): Based on age & severity.
- < 3 months: Hospitalize & give IV antibiotics (Ceftriaxone or Cefotaxime + Amikacin).
- > 3 months (Toxic): Hospitalize & IV antibiotics.
- > 3 months (Non-toxic): Oral antibiotics (Cefixime, Amoxiclav) for 7-14 days.
Imaging Protocol: To detect renal scarring & VUR.
- Ultrasound (USG): For ALL children with their first febrile UTI.
- MCU (VCUG): If USG is abnormal, atypical UTI, or recurrent UTI.
- DMSA Scan: Gold standard for renal cortical defects (scarring). Done 4-6 months after acute infection.

⭐ High-Yield: A DMSA scan is the most sensitive imaging modality for detecting acute pyelonephritis and subsequent renal scarring. It should be performed 4-6 months after the UTI episode to differentiate acute changes from permanent scars.

High‑Yield Points - ⚡ Biggest Takeaways

E. coli is the most common causative organism in pediatric UTIs.

The gold standard for diagnosis is a urine culture; suprapubic aspiration is the most accurate collection method in infants.

MCU/VCUG is the investigation of choice to detect Vesicoureteral Reflux (VUR), the most common predisposing factor.

A DMSA scan, performed 4-6 months post-infection, is the best test for identifying renal scarring.

Infants < 2 months with a febrile UTI require hospitalization and IV antibiotics.

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