Abdominal Distention and Constipation
Bradford P. Smith
Abdominal distention may be caused by feed, fluid, gas, feces, or a neoplasm (Boxes 7.13 and 7.14). Pregnancy or extreme obesity may also result in an enlarged abdomen.
The physical examination should determine which of these is the most likely cause. Often in ruminants the distention can be seen as primarily left sided, right sided, or bilateral. For example, bloat in ruminants results in a characteristic high left-sided gas distention. It may be primary or associated with vagal indigestion, tetanus, or hypocalcemia. With vagal indigestion the rumen■ BOX 7.11
■ BOX 7.13
Causes of Blood, Fibrin, or Mucus in Feces of the Horse
Common Causes
Foreign body
Rectal tear or trauma
Intussusception
Blister beetle (cantharidin) toxicity
Colitis, unknown cause
Salmonellosis
Less Common Causes
Purpura hemorrhagica
Small strongyle infection (cyathostomiasis) Colorectal polyps
Eosinophilic gastroenteritis
Acorn or oak poisoning
Arsenic toxicity
Organophosphate toxicity
Warfarin poisoning or other coagulation disorder Mycotoxicoses
Besnoitiosis (globidiosis) (exotic)
■ BOX 7.12
Causes of Blood, Fibrin, or Mucus in Feces of Ruminants
Common Causes
Foreign body Intussusception
Coccidiosis Salmonellosis
Less Common Causes
Rectal tear or trauma Rectal examination trauma Volvulus, root of mesentery Malignant catarrhal fever
Enterotoxemia Bovine viral diarrhea
Arsenic toxicity Abomasal torsion
Warfarin poisoning or other coagulation disorder Castor bean (Ricinus) poisoning
Tung tree (Aleurites) poisoning Solanum (nightshade, potato) poisoning Sesbania (rattlebox) poisoning
Bracken fern
becomes enlarged and fluid filled, often giving a pear shape to the abdomen as it is viewed from the rear, or a pear shape on the right and an apple shape on the left (“papple” shape) if some degree of bloat is also present.
Hypocalcemia and hypokalemia contribute to ileus and may result in constipation and abdominal enlargement. In sheep, abomasal impaction and enlargement associated with abomasal emptying defects can result in an enlarged abdomen with decreased food intake. When a mass (most commonly an abscess, a tumor, or fat necrosis [cattle only]) obstructs fecal passage, abdominal enlargement can become severe. With obstructive disease, some degree of colic is almost always present. A ruptured bladder results in a large fluid-filled abdomen, but constipation is not an obvious sign.Causes of Abdominal Distention and Constipation in Horses
Common Causes
Ileus impaction
Intestinal foreign body such as enterolith (see Colic) Peritonitis
Intestinal obstruction, impaction, or gas (see Colic) Necrotizing enterocolitis (foals)
Torsion or volvulus of gut (see Colic) Sudden decrease in exercise
Less Common Causes
Pregnancy
Pelvic mass (abscess, tumor) Cecal tympany (see Colic) Hernia, obstructive (see Colic) Intussusception (see Colic)
Uncommon Causes
Anticholinergics
Opiates Intrinsic colonic nerve dysfunction
Anorectal pain Perineal hernia
Hypokalemia Tetanus
Hypocalcemic tetany Intramural hematomas on gut Propylene glycol toxicity Grass sickness (exotic)
The most common causes of decreased fecal output in ruminants and horses are decreased feed intake and dehydration. In such cases the animal will appear gaunt or have a relatively empty abdomen or rumen. Horse feces in cases of prolonged transit are often covered with a layer of tenacious, thick, yellow mucus. When a functional obstruction (ileus, vagal indigestion) or physical obstruction (impaction, foreign body, displaced intestine, fat necrosis) occurs as a cause of constipation, the abdomen is more likely to appear normally full or to become distended. Rectal examination is of great help in determining whether a mass or an obstruction exists because loops of distended small bowel can sometimes be palpated in the latter case.
Radiographs and ultrasound may be valuable to help determine the cause of abdominal distention in foals, calves, and small ruminants. Increased gastrointestinal gas may result in abdominal distention. Abomasal bloat and necrotizing enterocolitis in young animals may best be confirmed with lateral abdominal radiographs.
Dehydration may also result in dry feces but not in abdominal enlargement. When constipation is present and feces are drier than normal, rehydration and correction of hypocalcemia, hypokalemia, and any existing acid-base abnormalities are important parts of correction of the constipation. Other nonspecific therapies for functional constipation include laxatives, cathartics, and cholinergic drugs. When treating constipation, which is usually a secondary problem, it is important to simultaneously attempt to diagnose the primary disease.
In ruminants, when abdominal distention involves the rumen or is caused by pregnancy or obesity, colic is absent. When abdominal distention is the result of obstruction from the pylorus distal, colic is usually present. Abdominal distention and constipation are frequently accompanied by colic in the horse, regardless of anatomic site involved (review the approach to colic).
■ BOX 7.14
■ BOX 7.15
Causes of Abdominal Distention and Constipation in Ruminants
Common Causes
Pregnancy Obesity
Vagal indigestion Grain overload
Bloat
Ileus
Cecal volvulus or dilation with ileus Peritonitis, traumatic or other cause Fat necrosis involving rectum or colon Ruptured bladder (uroperitoneum) Intestinal obstruction
Pelvic mass (abscess, tumor) Hypocalcemia
Omasal obstruction or foreign body
Less Common Causes
Anticholinergics Intussusception
Abomasal volvulus Abomasal impaction
Tetanus Abomasal bloat (calf) Necrotizing enterocolitis (calf)
Uncommon Causes
Hydrops Ascites
Torsion of descending colon
Internal herniation, especially diaphragmatic hernia involving reticulum
Displacement of intestine to left of rumen Stenosis of duodenum
Adhesions of intestine Bovine leucosis
Intestinal volvulus Atresia of anus, colon, rectum, or intestine Abomasal adenocarcinoma
Omental bursitis Perforated abomasal ulcer
Zinc toxicity Crude oil toxicity
Diesel fuel toxicity Propylene glycol toxicity
Larkspur poisoning