when detection is delayed or the rupture occurs spontaneously , it sometimes resembles acute kidney injury because ascites , oliguria and increasing serum creatinine levels are observed in patients with intraperitoneal urinary leakage . a 37-year - old woman presented with post - operative acute abdominal distension and an increasing serum creatinine level 7 days after total abdominal hysterectomy for uterine myoma . her serum creatinine and urea nitrogen levels were elevated , but the serum beta2-microglobulin level was within normal limits . the patient had no history of kidney disease , and her serum creatinine level on post - operative day 1 was normal ( 0.76 mg / dl ) . sodium , potassium and chloride levels in the ascitic fluid were 37 , 19 and 76 meq / l , respectively , which differed markedly from the serum electrolyte levels ( table 1 ) . laboratory findings of two cases of intraperitoneal urine leakage because these symptoms may also be caused by drug - induced nephropathy , all medications were stopped . however , no decrease in ascites or in the serum creatinine level was observed . since the patient s urine volume had decreased , a urinary catheter was inserted . the perforation was closed surgically , and a subsequent retrograde cystography did not reveal urinary leak . retrograde cystography exhibiting bladder perforation in case 1 ( a ) and case 2 ( b ) . a 70-year - old woman with a history of radiotherapy for cervical cancer 16 years earlier presented with progressive abdominal distension over a 2-week period . on admission sodium , potassium and chloride levels in the ascitic fluid were 21 , 23 and 78 meq / l , respectively , which differed from the serum electrolyte levels ( table 1 ) . after placement of the catheter in the bladder , the ascites disappeared , and the serum creatinine level decreased to the normal range . we performed retrograde cystography , but bladder perforation was not detected . because the patient s condition had improved , she was discharged from the hospital . three months after discharge , the patient was re - admitted with massive ascites and an increasing serum creatinine level . to determine the cause of serum creatinine elevation , we performed technetium-99 m diethylenetriaminepentaacetic acid ( tc-99 m dtpa ) renography , which showed extravasation of tc-99 m dtpa into the peritoneal cavity . retrograde cystography revealed a small perforation in the bladder ( figure 1b , arrow ) . intraperitoneal urinary leakage is characterized by an increase in the serum creatinine level caused by reabsorption of creatinine in the urine through the peritoneal membrane , oliguria and ascites . because most cases of intraperitoneal urinary leakage are the result of blunt trauma , leakage without obvious trauma the incidence of bladder injury after total abdominal hysterectomy is 0.1% . because most bladder injuries are identified intraoperatively , delayed appearance of urinary leakage however , the literature includes one report of delayed intraperitoneal urinary leakage after caesarean section . although spontaneous bladder perforation is uncommon , several cases have been reported in association with intravesicular obstruction , infectious lesion of the bladder , bladder diverticulum , bladder carcinoma , chemotherapy , and alcohol or substance abuse . therefore , acute kidney injury with massive ascites and peritonitis should be distinguished from urinary leakage . however , our two cases had abdominal pain , but rebound tenderness , which is a sign of peritonitis , was not noted . because bladder rupture without signs of peritonitis has been reported , symptoms of peritonitis may sometimes be unclear . although a correlation between serum and ascitic electrolyte levels has not been clearly established , some papers have reported this correlation [ 79 ] . sodium , potassium and chloride levels in ascitic fluid are nearly identical to those in serum ( ascites vs. serum ; sodium 133.1  6.6 vs. 131.8  6.3 mmol / l , potassium 4.1  0.8 vs. 4.3  0.9 mmol / l and chloride 107.2  7.6 vs. 101  7 mmol / l ) in cirrhosis patients . in peritoneal dialysis patients , electrolyte levels in peritoneal dialysate that are retained longer than 24 h are nearly identical to those in serum ( peritoneal dialysate vs. serum ; sodium 141.4 vs. 140.6 meq / l , potassium 4.7 vs. 5.1 meq / l and chloride 108.5 vs. 102.7 meq / l ) . another report noted that the ratio of sodium , potassium and chloride between serum and transudates which include ascites is 0.95 , 0.740.80 , and 0.950.99 , respectively . however , in our two cases , the ascitic sodium , potassium and chloride levels differed markedly from their serum levels . both serum beta2-microglobulin and creatinine levels are usually elevated in patients with acute kidney injury . this was not the case in our first patient , and this discrepancy may be a clue to the presence of intraperitoneal urinary leakage . the reason for this discrepancy has not been elucidated ; however , beta2-microglobulin , due to its larger molecular size , may not be absorbed through the peritoneal membrane similar to creatinine . in addition , although we did not measure urea nitrogen and creatinine in the ascitic fluid , the higher levels in ascites than in the blood are additional clues suggesting the possibility of intraperitoneal urinary leakage . in summary , we report two cases with intraperitoneal urinary leakage resembling acute kidney injury . these cases suggest that bladder perforation should be considered in the differential diagnosis of acute kidney injury with massive ascites .
ascites , oliguria and increasing serum creatinine levels are often noted in patients with acute kidney injury . 
 however , these presentations are also observed in patients with intraperitoneal urinary leakage . 
 bladder perforation without obvious trauma is sometimes mistaken for acute kidney injury . 
 we report two cases of bladder perforation resembling acute kidney injury . 
 the first case was a 37-year - old woman with delayed intraperitoneal urinary leakage following total abdominal hysterectomy , and the second was a 70-year - old woman with spontaneous bladder perforation . 
 although the initial diagnosis in both cases was acute kidney injury , rupture of the urinary bladder was later identified .