Ascites in a 17-Year-Old with Complicated UTI and Bilateral Pelvocaliectasia
The ascites in this patient is most likely uroperitoneum (urinary ascites) caused by urinary tract perforation or leakage secondary to the obstructive uropathy from bilateral pelvocaliectasia. This represents a urological emergency requiring immediate diagnostic confirmation and intervention.
Primary Mechanism
Bilateral pelvocaliectasis creates increased intrapelvic pressure that can lead to forniceal rupture or bladder perforation, resulting in urine leaking into the peritoneal cavity. 1, 2 The combination of infection and obstruction significantly increases this risk, as infected urine under pressure seeks alternative drainage pathways.
Key Pathophysiologic Points:
Obstructive uropathy from bilateral pelvocaliectasis causes elevated intrarenal pressures that can rupture the renal fornices, allowing urine to extravasate into the retroperitoneum and subsequently into the peritoneal cavity 2
Infected obstructed systems are particularly prone to perforation because inflammation weakens tissue integrity while pressure continues to build 3
Bladder perforation or fistula formation can occur spontaneously in the setting of severe infection, particularly with complicated UTIs involving anatomical abnormalities 1, 4
Diagnostic Confirmation
Measure creatinine and urea levels in both the ascitic fluid and serum immediately. 4 An ascites-to-plasma creatinine ratio >5:1 confirms uroperitoneum, as urinary creatinine is substantially higher than plasma creatinine when urine accumulates in the peritoneal cavity.
Imaging Strategy:
CT urography with ultra-late excretory phase imaging (15-30 minutes post-contrast) is the optimal diagnostic test, as it provides complete visualization of the entire urinary tract and can directly demonstrate contrast extravasation into the peritoneal cavity 1
CT cystography may be needed if bladder perforation is suspected, involving retrograde instillation of diluted contrast into the bladder followed by CT imaging at maximal distension 3
Standard CT abdomen/pelvis with IV contrast alone is insufficient because it lacks the delayed imaging necessary to detect subtle urinary leakage 3
Clinical Context
This 17-year-old female has complicated UTI by definition due to the presence of bilateral anatomical abnormalities (pelvocaliectasis) and likely obstruction. 3, 5 The European Association of Urology guidelines explicitly classify UTIs with obstruction at any site in the urinary tract as complicated infections requiring different management than uncomplicated UTIs. 3
Critical Complications to Address:
Bilateral obstruction with infection can rapidly progress to urosepsis and requires urgent decompression via nephrostomy tubes or ureteral stents 3
Uroperitoneum itself causes peritonitis and can lead to electrolyte abnormalities (hyperkalemia, metabolic acidosis) from reabsorption of urinary constituents across the peritoneum 4
The underlying cause of bilateral pelvocaliectasis must be identified—possibilities include bilateral ureteral obstruction from stones, strictures, or extrinsic compression 2, 6
Immediate Management Priorities
Obtain urine culture with susceptibility testing before initiating empiric broad-spectrum parenteral antibiotics (such as ceftriaxone 2g daily or piperacillin-tazobactam 4.5g three times daily), as complicated UTIs have higher rates of multidrug-resistant organisms. 3 However, do not delay antibiotics waiting for culture results in a septic patient.
Urological consultation for urgent drainage of the obstructed collecting systems is mandatory—this takes precedence over antibiotic therapy alone, as "appropriate management of the urological abnormality or the underlying complicating factor is mandatory" per EAU guidelines. 3
Paracentesis for symptomatic relief and diagnostic fluid analysis should be performed, with consideration for continuous drainage via pigtail catheter if large volume uroperitoneum is confirmed. 2
Treatment Duration:
- Antimicrobial therapy should continue for 7-14 days for complicated UTI (14 days recommended when anatomical abnormalities are present), but duration must be closely related to successful treatment of the underlying obstruction 3
Common Pitfalls
Do not assume ascites is from liver disease, heart failure, or malignancy without first considering urinary tract pathology in any patient with known urological abnormalities or recent UTI. 4 The history of bilateral pelvocaliectasis and active UTI should immediately raise suspicion for uroperitoneum.
Do not perform standard abdominal imaging without urographic protocol—conventional CT or ultrasound may show ascites but will miss the urinary source without delayed excretory phase imaging. 1
Do not delay urological decompression while attempting medical management alone—infected obstructed systems require drainage, and antibiotics cannot adequately penetrate obstructed infected tissue. 3