A 41-year-old woman is evaluated on postoperative day 3 for diffuse abdominal pain, progre… — USMLE Step 2 CK

A 41-year-old woman is evaluated on postoperative day 3 for diffuse abdominal pain, progressive abdominal distention, and nausea. She recently underwent an uncomplicated total laparoscopic hysterectomy for symptomatic leiomyomas and severe pelvic endometriosis. Her temperature is 38.3°C (100.9°F), pulse is 102/min, and blood pressure is 112/74 mm Hg. Physical examination shows a significantly distended abdomen with shifting dullness and diffuse tenderness to palpation. Bowel sounds are hypoactive. Her surgical incisions are clean and intact. The patient reports voiding small amounts of urine frequently since her indwelling urinary catheter was removed 48 hours ago. Laboratory studies show a leukocyte count of 14,500/mm³, a blood urea nitrogen of 46 mg/dL, and a serum creatinine of 2.8 mg/dL. Her preoperative serum creatinine was 0.7 mg/dL. Which of the following is the most appropriate next step in management?

Retrograde CT cystographyAnswer
B
Nasogastric tube insertion and bowel rest
C
Empiric administration of broad-spectrum intravenous antibiotics
D
Renal and bladder ultrasonography
E
Urinalysis and urine culture

Answer

Retrograde CT cystography

This patient's presentation of progressive abdominal distention, shifting dullness (ascites), fever, and apparent acute kidney injury following a laparoscopic hysterectomy is highly suspicious for an unrecognized intraperitoneal bladder injury. The bladder dome is particularly vulnerable during the dissection of the vesicouterine fold, especially when pelvic anatomy is distorted by severe endometriosis. If a cystotomy goes unrecognized, urine continuously leaks into the peritoneal cavity, causing a severe chemical peritonitis (manifesting as abdominal pain, ileus, and fever). The peritoneal membrane rapidly reabsorbs the urea nitrogen and creatinine from the pooled urine, leading to pseudo-renal failure (elevated BUN and Cr) despite intrinsically normal kidney function. The diagnostic test of choice is retrograde CT cystography. This involves instilling radiopaque contrast directly into the bladder via a urinary catheter to maximally distend it, which effectively visualizes the leak into the peritoneal cavity.

Step-by-Step Solution

Analyze the postoperative clinical presentation and physical examination.

The patient has fever, abdominal pain, ileus, and new-onset ascites (shifting dullness) on postoperative day 3 following a laparoscopic hysterectomy for severe endometriosis.

Identifying the timeline and key physical findings helps narrow the differential for post-hysterectomy complications.

Evaluate the laboratory results in the context of the clinical picture.

There is a dramatic rise in serum creatinine (0.7 to 2.8 mg/dL) and BUN, appearing as severe acute kidney injury.

Ascites combined with apparent acute kidney injury strongly suggests that urine is leaking into the peritoneal cavity, where urea and creatinine are rapidly reabsorbed into the bloodstream (pseudo-renal failure).

Determine the most likely injured anatomical structure and the best diagnostic modality.

The bladder dome is the most likely injured structure, causing an intraperitoneal leak. Retrograde CT cystography is the diagnostic test of choice.

Retrograde instillation of contrast under pressure maximally distends the bladder, reliably demonstrating the precise location and extent of the defect.

Key Concept

Intraperitoneal bladder rupture typically presents with delayed-onset ascites, chemical peritonitis, and pseudo-renal failure (elevated BUN and creatinine due to peritoneal reabsorption). It is diagnosed using retrograde CT cystography.

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