Equis ISSN 2398-2977

Abdomen: uroperitoneum

Contributor(s): David Moll, Graham Munroe, Carla Sommardahl


  • Uroperitoneum is presence of free urine in the peritoneal cavity.
  • Cause: damage or congenital malformations of the urinary system.
  • Signs: depression, abdominal pain and distension.
  • Most often seen in young foals, within a week of birth, but can be seen in adult horses and generally follows damage to the urinary system that may be secondary to urolithiasis or foaling.
  • Diagnosis: presence of urine in a peritoneal fluid aspirate.
  • Treatment: initial stabilization of the patient, followed by surgical repair of the damaged or malformed area.
  • Prognosis: guarded. In foals the survival rate is approximately 60%.



  • Most common form is seen in approximately 1% of foals, mainly Thoroughbred males, who rupture their bladders   Bladder: rupture  during the birth process due to the pressure exerted on the bladder (predisposed by long urethra) or as a consequence of urachal leakage secondary to infection of umbilical/urachal structures.
  • Approximately 1% of foals with uroperitoneum have it as a result of a congenital malformation of bladder or ureters. The bladder defects are only distinguishable from the ruptured bladder foal   Bladder: rupture  at surgical intervention and are treated surgically.
  • Urethral defects can be uni/bilateral and usually involve the proximal one third. Urine accumulates retroperitoneally initially.
  • The disease occurs occasionally in adult horses, and is usually seen secondary to either injuries sustained at foaling, or blockage of the urethra with uroliths and consequent bladder rupture   Bladder: rupture  .

Predisposing factors

  • Rupture of the bladder   Bladder: rupture  is usually along the dorsal surface where it is weakest in newborn foals.
  • Malformation of the bladder or ureters causes problems in young foals.
  • In adults predisposing factors are recent foaling with bladder damage, or urolithiasis.


  • Damage/malformation of the ureters, bladder or urethra results in leakage of urine into the peritoneal cavity.
  • This causes a chemical peritonitis, the irritant effects of the urine causing inflammation, given that the urine is sterile. If cystitis   Bladder: cystitis - bacterial  or pyelonephritis is also present a bacterial peritonitis   Abdomen: peritonitis  may result.
  • Loss of urine into the peritoneum reduces the amount passed normally.
  • Presence of urine in the peritoneum causes increased permeability of the peritoneal membrane, and loss of fluid and cells into the peritoneum.
  • Hypovolemia and shock can result.
  • Incomplete bladder/ureteral margin allows urine leakage into peritoneum.
  • Chemical effect causes inflammation of peritoneum, with consequent partition of fluid into peritoneum.
  • Abdominal pain and distension, with straining due to inflammation can result.
  • Cardiovascular and circulatory shock can follow.
  • Loss of sodium and chloride ions into peritoneum result in hyperkalemia   Blood: biochemistry - potassium  , hypochloremia   Blood: biochemistry - chloride  , hyponatremia   Hyponatremia    Blood: biochemistry - sodium  and metabolic acidosis   Acid-base imbalance  . Hypoglycemia   Hypoglycemia    Blood: biochemistry - glucose  is often common.
  • Hyperkalemia may   →   cardiac arrhythmias   Heart: sinus dysrhythmia  .
  • Dehydration and septicemia   Foal: neonatal septicemia syndrome  /toxemia may also occur.


  • Disease is generally seen in foals within a week of birth. In adults, also, symptoms take from a day to a week from the original injury to come to light.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Love E J (2011) Anaesthesia in foals with uroperitoneum. Equine Vet Educ 23 (10), 508-511 Wiley Online Library.
  • Castagnetti C et al (2010) Urethral and bladder rupture in a neonatal colt with uroperitoneum. Equine Vet Educ 22 (3), 132-138 VetMedResource.
  • Hawkins J F (2010) Evaluation and treatment of the foal with uroperitoneum. Equine Vet Educ 22 (3), 139-140 VetMedResource.
  • Wilkins P A (2004) Respiratory distress in foals with uroperitoneum: possible mechanisms. Equine Vet Educ 16 (6), 293-295 VetMedResource.
  • Wong D M, Leger L C, Scarratt W K & Kline K A (2004) Uroperitoneum and pleural effusion in an Americal Paint filly. Equine Vet Educ 16 (6), 290-293 VetMedResource.
  • Kablack K A et al (2000) Uroperitoneum in the hospitalised equine neonate - restrospective study of 31 cases, 1988-1997. Equine Vet J 32 (6), 505-507 PubMed.
  • Harvey J (1998) Uroabdomen in foals. Equine Vet Educ 10 (1), 21-25 VetMedResource.
  • Jean J, Marcoux M, Louf C F (1998) Congenital bilateral defect in the ureters of a foal. Equine Vet Educ 10 (1), 17-20 VetMedResource.
  • Brewer B (1990) Renal conditions of the newborn and older foal. Equine Vet Educ (3), 127-129 VetMedResource.

Other sources of information

  • Rose R J & Hodgson D R (1993) Manual of Equine Practice. W B Saunders. ISBN: 0 7216 3739 6.