A 31-year-old obese Caucasian female presents to the Emergency Department late in the evening for left lower quadrant pain that has progressively worsened over the last several hours. She describes the pain as sharp and shooting, coming and going. Her last bowel movement was this morning. She has also had dysuria and urgency. Her surgical history is notable for gastric bypass surgery 2 years prior and an appendectomy at age 9. She is sexually active with her boyfriend and uses condoms. Her temperature is 99.5 deg F (37.5 deg C), blood pressure is 151/83 mmHg, pulse is 86/min, respirations are 14/minute, BMI 32. On physical exam, she has left lower quadrant tenderness to palpation with pain radiating to the left groin and left flank tenderness on palpation. Her urinalysis shows 324 red blood cells/high power field. Her pregnancy test is negative. What is the next best step in management?

A KUB (kidneys, ureters and bladder) plain film

A 37-year-old woman presents to the Emergency Department after 8 hours of left sided flank pain that radiates to her groin and pelvic pain while urinating. Her medical history is relevant for multiple episodes of urinary tract infections, some requiring hospitalization, and intravenous antibiotics. In the hospital, her blood pressure is 125/83 mm Hg, pulse of 88/min, a respiratory rate of 28/min, and a body temperature of 36.5°C (97.7°F). On physical examination, she has left costovertebral tenderness and lower abdominal pain. Laboratory studies include a negative pregnancy test, mild azotemia, and a urinary dipstick that is positive for blood. Which of the following initial tests would be most useful in the diagnosis of this case?

Fractional excretion of sodium (FeNa+)

Contrast abdominal computed tomography

Blood urea nitrogen (BUN): serum creatinine (SCr) ratio

Following passage of a calcium oxalate stone, a 55-year-old male visits his physician to learn about nephrolithiasis prevention. Which of the following changes affecting urine composition within the bladder are most likely to protect against crystal precipitation?

Decreased calcium, increased citrate, decreased oxalate, increased free water clearance

Decreased calcium, increased citrate, increased oxalate, increased free water clearance

Increased calcium, increased citrate, increased oxalate, increased free water clearance

Decreased calcium, increased citrate, increased oxalate, decreased free water clearance

Decreased calcium, decreased citrate, increased oxalate, increased free water clearance

A 34-year-old female presents to her primary care physician with complaints of fevers, nausea/vomiting, and severe left flank pain that has developed over the past several hours. She denies any prior episodes similar to her current presentation. Physical examination is significant for a body temperature of 39.1 C and costovertebral angle tenderness. A urinalysis and urine microscopy are ordered. Which of the following findings on kidney histology would be expected in this patient?

Neutrophils filling the lumens of the renal tubules

Enlarged, hypercellular glomeruli with 'wire-looping' of capillaries

Interstitial fibrosis and lymphocytic infiltrate

Thickening of the capillaries and glomerular basement membrane

A 43-year-old man presents with acute-onset left flank pain for the past 6 hours. He describes the pain as severe, intermittent, colicky, and “coming in waves”, and he points to the area of the left costovertebral angle (CVA). He says he recently has been restricting oral liquid intake to only 2 glasses of water per day based on the advice of his healer. He also reports nausea and vomiting. The patient has a history of hypertension, gout, and type 2 diabetes mellitus. He is afebrile, and his vital signs are within normal limits. On physical examination, he is writhing in pain and moaning. There is exquisite left CVA tenderness. A urinalysis shows gross hematuria. Which of the following is the next best step in the management of this patient?

Non-contrast CT of the abdomen and pelvis

Contrast CT of the abdomen and pelvis

A 33-year-old woman comes to the emergency department because of severe right flank pain for 2 hours. The pain is colicky in nature and she describes it as 9 out of 10 in intensity. She has had 2 episodes of vomiting. She has no history of similar episodes in the past. She is 160 cm (5 ft 3 in) tall and weighs 104 kg (229 lb); BMI is 41 kg/m2. Her temperature is 37.3°C (99.1°F), pulse is 96/min, respirations are 16/min and blood pressure is 116/76 mm Hg. The abdomen is soft and there is mild tenderness to palpation in the right lower quadrant. Bowel sounds are reduced. The remainder of the examination shows no abnormalities. Her leukocyte count is 7,400/mm3. A low-dose CT scan of the abdomen and pelvis shows a round 12-mm stone in the distal right ureter. Urine dipstick is mildly positive for blood. Microscopic examination of the urine shows RBCs and no WBCs. 0.9% saline infusion is begun and intravenous ketorolac is administered. Which of the following is the most appropriate next step in management?

Extracorporeal shock wave lithotripsy

A 57-year-old man presents with acute-onset nausea and left flank pain. He says his symptoms suddenly started 10 hours ago and have not improved. He describes the pain as severe, colicky, intermittent, and localized to the left flank. The patient denies any fever, chills, or dysuria. His past medical history is significant for nephrolithiasis, incidentally diagnosed 10 months ago on a routine ultrasound, for which he has not been treated. His family history is unremarkable. The patient is afebrile, and his vital signs are within normal limits. On physical examination, he is writhing in pain and moaning. Severe left costovertebral angle tenderness is noted. Gross hematuria is present on urinalysis. A non-contrast CT of the abdomen and pelvis reveals a 12-mm obstructing calculus at the left ureterovesical junction. Initial management, consisting of IV fluid resuscitation, antiemetics, and analgesia, is administered. Which of the following is the best next step in the management of this patient?

Percutaneous nephrostolithotomy (PCNL)

Extracorporeal shockwave lithotripsy (ESWL)

A 56-year-old man is brought to the emergency department 25 minutes after he was involved in a high-speed motor vehicle collision where he was the unrestrained passenger. He has severe lower abdominal and pelvic pain. On arrival, he is alert and oriented. His pulse is 95/min, respirations are 22/min, and blood pressure is 106/62 mm Hg. Examination shows severe tenderness to palpation over the lower abdomen and over the left anterior superior iliac spine. There is no limb length discrepancy. Application of downward pressure over the pelvis shows no springy resistance or instability. Rectal examination is unremarkable. A focused assessment with sonography shows no free fluid in the abdomen. There is no blood at the urethral meatus. Placement of a Foley catheter shows gross hematuria. An x-ray of the pelvis shows a fracture of the left pelvic edge. Which of the following is the most appropriate next step in management?

External fixation of the pelvis

A 50-year-old man is brought to the emergency department because of a 3-day history of left flank pain. The patient has had two episodes of urolithiasis during the last year. He initially had pain with urination that improved with oxycodone. Over the past day, the pain has worsened and he has additionally developed fever and chills. He has hypertension and type 2 diabetes mellitus. He has smoked one pack of cigarettes daily for 20 years. He does not drink alcohol. His current medications include metformin and lisinopril. The patient appears ill and uncomfortable. His temperature is 39.1°C (102.3°F), pulse is 108/min, respirations are 22/min, and blood pressure is 90/62 mm Hg. The lungs are clear to auscultation. Cardiac examination shows no murmurs, rubs, or gallops. Examination of the back shows left costovertebral angle tenderness. Physical and neurologic examinations show no other abnormalities. Laboratory studies show: Hemoglobin 14.2 g/dL Leukocyte count 13,900/mm3 Hemoglobin A1c 8.2% Serum Na+ 138 mEq/L K+ 3.8 mEq/L Cl- 98 mEq/L Calcium 9.3 mg/dL Glucose 190 mg/dL Creatinine 2.1 mg/dL Urine pH 8.3 Urine microscopy Bacteria moderate RBC 6–10/hpf WBC 10–15/hpf WBC casts numerous Ultrasound shows enlargement of the left kidney with a dilated pelvis and echogenic debris. CT scan shows a 16-mm stone at the left ureteropelvic junction, dilation of the collecting system, thickening of the wall of the renal pelvis, and signs of perirenal inflammation. Intravenous fluid resuscitation and intravenous ampicillin, gentamicin, and morphine are begun. Which of the following is the most appropriate next step in the management of this patient?

Ureteroscopy and stent placement

A 70-year-old man with metastatic castration-resistant prostate cancer presents to the emergency department with severe back pain, bilateral lower extremity weakness (3/5 strength), and urinary retention that started 8 hours ago. He has known bone metastases and his PSA has been rising despite androgen deprivation therapy. MRI spine shows an epidural mass at T10 with severe spinal cord compression and near-complete canal obliteration. He is neurologically intact above T10. Radiation oncology, neurosurgery, and medical oncology are consulted. Evaluate the optimal management approach.

Emergent surgical decompression followed by radiation therapy

Corticosteroids, radiation therapy, and switch to next-line systemic therapy

Stereotactic radiosurgery as single-modality treatment

Palliative care consultation and comfort measures only given metastatic disease

High-dose corticosteroids and emergent radiation therapy alone

Kidney stone management for USMLE Step 2 CK: High-Yield Surgery Lessons

💎 Stone Cold Science

Nephrolithiasis results from urine supersaturation with stone-forming solutes, leading to crystal precipitation and growth. Key factors include low urine volume, abnormal pH, and metabolic disturbances.

Urine microscopy of normal and abnormal crystals

Stone Type	Composition	Cause/Risk Factors	Urine pH	X-ray	Treatment
Ca Oxalate	$CaC_2O_4$	Most common. Hypercalciuria, hyperoxaluria (Crohn's)	↓ or neutral	Opaque	Thiazides, citrate
Ca Phosphate	$Ca_3(PO_4)_2$	Hypercalciuria, Renal Tubular Acidosis (Type 1)	↑ (Alkaline)	Opaque	Treat RTA
Struvite	$MgNH_4PO_4$	Urease+ UTI (Proteus, Klebsiella); staghorn calculi	↑ (Alkaline)	Opaque	Abx, stone removal
Uric Acid	Uric Acid	Gout, ↑cell turnover (leukemia), dehydration	↓ (Acidic)	Lucent	Allopurinol, alkalinize
Cystine	Cystine	Genetic defect (cystinuria), hexagonal crystals	↓ (Acidic)	Faintly opaque	Alkalinize, penicillamine

😫 Clinical Manifestations - The Agony of the Stone

Renal Colic: Acute, severe, colicky flank pain. Patients are often writhing, unable to find a comfortable position.
Pain Radiation: Follows the stone's path.
- Upper Ureter: Flank/CVA pain.
- Mid Ureter: Radiates anteriorly to groin, testes, or labia.
- Distal Ureter (UVJ): Lower quadrant pain, mimics UTI with urgency/frequency.
Associated Symptoms:
- Hematuria (gross or microscopic).
- Nausea & vomiting (shared autonomic innervation).
Physical Exam:
- Costovertebral angle (CVA) tenderness.

⭐ The inability to find a comfortable position is a classic sign, distinguishing it from peritonitis where patients lie still.

🕵️‍♂️ Diagnosis - Finding the Culprit

Initial Workup:
- Urinalysis (UA): Essential first step. Look for hematuria (microscopic/gross).
- Urine pH: Suggests stone type.
  - pH < 5.5: Uric acid, Cystine stones.
  - pH > 7.2: Struvite (infection) stones.
- Basic Metabolic Panel (BMP): Assess renal function (BUN/Cr).
Imaging Modalities:
- Non-contrast CT (Abdomen/Pelvis): Gold standard. High sensitivity & specificity.
- Ultrasound (US): Preferred in pregnant patients & children to avoid radiation.
- KUB X-ray: Monitors radiopaque stones (e.g., Calcium).

CT showing hydronephrosis and distal ureteral stone

⭐ Non-contrast helical CT is the single best test for diagnosing acute flank pain suspicious for nephrolithiasis in non-pregnant adults. It identifies stone size, location, and degree of obstruction.

💎 Management - Crush, Grab, Blast

Medical Expulsive Therapy (MET): For uncomplicated stones <10 mm.
- Hydration, analgesia (NSAIDs), and alpha-blockers (e.g., Tamsulosin).
Extracorporeal Shock Wave Lithotripsy (ESWL): "Blast"
- Non-invasive acoustic pulses. Best for stones <2 cm in the renal pelvis/upper ureter.
- ⚠️ Contraindicated in pregnancy, bleeding diathesis.
Ureteroscopy (URS): "Grab"
- Endoscopic approach; laser fragments stone, basket retrieves.
- Primary for mid-to-distal ureteral stones.
Percutaneous Nephrolithotomy (PCNL): "Crush"
- Invasive access through the flank. For large stones (>2 cm) or staghorn calculi.

⭐ High-Yield: For stones 1-2 cm, the choice between ESWL and ureteroscopy depends on location. ESWL is preferred for renal pelvis/upper ureter stones, while ureteroscopy is better for mid/distal ureteral stones and offers a higher stone-free rate.

⚡ Biggest Takeaways

Non-contrast CT is the gold standard for diagnosis; use ultrasound in pregnant patients or children.

Stones < 5 mm typically pass spontaneously; manage with hydration, pain control, and medical expulsive therapy (tamsulosin).

Stones > 10 mm rarely pass and usually require intervention.

ESWL is for smaller stones (< 2 cm) in the renal pelvis or upper ureter.

Ureteroscopy is preferred for mid-to-distal ureteral stones.

PCNL is reserved for large stones (> 2 cm) or staghorn calculi.

Urosepsis, AKI, or anuria require urgent decompression via stent or nephrostomy tube.

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