Thank you. This is called hematochezia and can result from more disorders than I could list in this venue. In most cases, a colitis is found in a young dog such as Lilah. I'll post a synopsis of colitis for you below but whatever the cause, her two days of anorexia, vomiting, and hematochezia should prompt her being attended to by her vet at your earliest convenience. Please peruse the synopsis and then return to our conversation with further questions or concerns if you wish...
The presence of red blood on the surface of or admixed into the stool
Species, Age, Sex
Dependent on underlying cause
- Neoplasia more likely in older animals
- Histiocytic ulcerative colitis: dogs < 2 years old
- Perineal hernia: adult/older, male intact dogs
The most common risk factor for hematochezia is colitis of any cause. Neoplasia is less commonly responsible. Coagulopathies are a rare cause of hematochezia.
Clinically significant anemia very uncommonly occurs as a result of hematochezia.
History, Chief Complaint
- Concurrent mucus in the stool, tenesmus (both are common), painful defecation, “scooting” behavior, licking/chewing/scratching the perineum are common manifestations of colonic or anorectal disease.
- Animals with isolated hematochezia rarely present signs of systemic illness.
- Weight loss and inappetence can occur with concurrent small-intestinal or pancreatic disease, histiocytic ulcerative colitis, or neoplasia.
Physical Exam Findings
- Generally clinically healthy
- The perianal area may be soiled with blood, fecal material, and/or mucus.
- The anus may be inflamed, ulcerated, or painful.
- A mass (neoplasm), swelling (anal sac abscess, perineal hernia, or neoplasm), or fissure (perianal fistula) around the anus may be visible.
- A digital rectal examination is essential in any patient with hematochezia (intraluminal or extraluminal mass, stricture, anal sac mass or abscess, pain, melena).
Etiology and Pathophysiology
- The blood is fresh (undigested), localizing the problem to the descending colon, rectum, or anus.
- Conversely, melena represents oxidized blood as seen with digested blood. Rarely, colonic disorders may produce melena, instead of hematochezia, if colonic transit times are substantially increased (e.g., constipation).
- Evaluation begins with history, physical exam, and digital rectal exam.
- In otherwise well animals with normal physical exam findings, diagnostic testing can begin with fecal analysis and/or response to nonspecific, supportive treatment.
- Further diagnostic evaluation is required in animals with signs of systemic illness, physical exam abnormalities, bleeding diathesis, and/or chronic/recurrent hematochezia.
- Anus (e.g., anal sac disorders, perianal fistula, neoplasia, trauma)
- Rectum and colon (e.g., colitis [most common], parasites, neoplasia, stress-associated)
- Visual and digital anorectal examination, including anal sac palpation
- Fecal flotation and direct examination for parasites
- Fecal smear, culture for fecal pathogens, Clostridium enterotoxin detection
- Results of trial therapy
Advanced or Confirmatory Testing
Further diagnostic evaluation is required in animals with signs of systemic illness, physical exam abnormalities, bleeding diathesis, and/or chronic/recurrent hematochezia.
- Serum biochemistry profile
- Coagulation profile
- Abdominal radiographs, ultrasound
Initial therapy consists of dietary change, broad-spectrum dewormer, and an antibiotic to control bacterial overgrowth. Unresponsive chronic cases may benefit from referral to a specialist for colonoscopy.
Acute General Treatment
Nonspecific trial therapy can be attempted in an animal without systemic signs:
- Dietary modification as dictated by underlying disorder
- Broad-spectrum anthelmintic (e.g., fenbendazole 50 mg/kg PO q 24h × 3 days)
- Trial course of metronidazole (e.g., 7.5-10 mg/kg PO q 12h × 10 days), or tylosin (10 mg/kg PO q 8h for 21 days as treatment trial if suspecting inflammatory bowel disease, or 20 mg/kg PO q 12h for clostridial colitis), sulfasalazine (dogs: 20-40 mg/kg PO q 8h for 14-21 days, then taper by 25%-30% q 14-21 days; cats [use with caution given salicylate sensitivity]: 10-20 mg/kg PO q 24h maximum of 10 days, then taper to lowest effective dose/discontinue)
Specific treatment depends on the underlying disease.
Prognosis & Outcome
Dependent on underlying disease