Page 979 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

954 CHAPTER 7

VetBooks.ir 7.37 7.38

Fig. 7.37 Bladder rupture in a foal. Note other Fig. 7.38 Abdominal distension in a foal with
erosions on the bladder mucosa caused by cystitis. uroperitoneum. The foal’s acid–base status is severely
affected, causing depression.

circumferentially around the bladder. The long and 7.39
narrow urethra in colts resists the pressure that is put
on the bladder during parturition and predisposes
the weak bladder wall of the neonate to rupture.
Urachal infection may also predispose to uroperi-
toneum. In adult horses, uroperitoneum develops
secondary to urethral obstruction, trauma, urinary
catheterisation and, in mares, during dystocia.
Rupture of the bladder (Fig. 7.37), urachus, ure-
ter or renal pelvis may result in leakage of urine into
the peritoneal cavity. As urine accumulates in the
abdomen, azotaemia, hyperkalaemia, hyponatrae-
mia, hypochloraemia and metabolic acidosis develop.
These abnormalities arise from the equilibration of
urine electrolytes and water across the peritoneal
membrane, allowing for loss of sodium and chlo- Fig. 7.39 A foal with uroperitoneum strains
ride, which move into the abdominal fluid/urine, to urinate. Other diseases, prematurity, gender,
and retention of potassium, which diffuses from hospitalisation and frequent handling predispose foals
the abdominal fluid/urine. Urea readily diffuses to bladder rupture.
across the peritoneal surface. Creatinine is a larger
molecule and diffuses much more slowly across the urinary tract rupture and uroperitoneum. A fluid
peritoneal surface. The presence of urine in the peri- wave may be felt, or a sloshing sound heard on suc-
toneal cavity also causes chemical peritonitis. cussion of the abdomen. Acid–base disturbance
produces depression, anorexia, tachycardia and
Clinical presentation tachypnoea. Respiratory distress can develop with
Abdominal discomfort, abdominal distension severe abdominal distension, particularly in foals.
(Fig. 7.38) and straining to urinate are often If the disease is not treated, shock and collapse will
observed (Fig. 7.39). Little to no urine is passed. develop. Severe tachycardia may be present with
Voiding of a small amount of urine does not exclude severe hyperkalaemia.