This document discusses the differential diagnosis of diarrhea in small and large intestines. It defines diarrhea and outlines key clinical signs that can indicate the location and underlying cause. For small intestine diarrhea, potential causes include dietary issues, infections, inflammatory/immune diseases, and idiopathic conditions. Large intestine diarrhea may result from similar causes like diet, infections, inflammation, and cancer, as well as obstructions, drugs/toxins, and stress. The document provides extensive lists of specific disorders, pathogens, medications, and toxins that commonly contribute to diarrhea in each intestinal region.

1. Veterinary Teaching Hospital
Airlangga University
Small Animal Practice
Differential
Diagnose

2. Diarrhea
• Diarrhea is define simply as passage of feces that
contain an excess amount of water. This results in an
abnormal increase in stool liquidity and weight. In
some patients there may simply be an increase in
frequency of defecation.
• Diarrhea has also been described in broad, simple
terms as “the too rapid evacuation of too loose
stools.”
• Definitions notwithstanding, however, it is most
important that the clinician carefully determine
exactly what the owner means when the term
diarrhea is used.
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3. Diarrhea
• Small intestine diarrhea
• Large intestine diarrhea
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4. Clinical Signs
Small intestine
Large intestine
Mucous
Rarely present
Frequently present
Volume
Increased
Normal to decreased
Feces
Quality of stool
Shape
Steatorrhea
Color
Melena
Hematochezia
Varies from nearly formed to quiet watery.
Loose to nearly formed. Mucus may be absent or
Often appears soft formed (“cowpile”). Undigested be present in small amounts, or constitute nearly
food or fat droplets or globules may be
the entire volume of material expelled. No
present. Malodorous
undigested food.
Vary, depends on amount of water present in
feces
Normal, reduced in diameter (narrowed)
Present with maldigestive/malabsorptive
disorders
Absent
Considerable variation—tan to dark brown, black
(not always indicative of melena), grayish brown.
May be altered by certain medications
Variable—usually brown, may be nearly clear
(increasedmucus) or laced with bright-red blood
Maybe present -- black, tarry stool
Absent
Absent, except in HGE syndrome
Maybe present
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5. Clinical Signs
Small intestine
Large intestine
Frequency
Usually increased to 2-4 times a day but may
remain normal in some patients
Almost always increased. May be as frequent
as 3-10 times per day (average 3-5). The
combination of increased frequency of
defecation and passage of decreased
amounts of stool strongly suggests large
intestinal involvement
Dyschezia
Absent
Frequent in dogs, less common in cat
Tenesmus
Absent
Frequent in dogs, less common in cat
May be present in cases of acute severe
enteritis, with rapid transit of large volumes of
fluid through the gastrointestinal tract
Frequent. Common reason for owner being
awakened during the night to allow a dog
outdoors to defecate. Often
Defecation
Urgency
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6. Clinical Signs
Small intestine
Large intestine
Vomit
Common in patients with inflammatory
bowel disorders and acute infectious disorders
May occur in 30%-35% of patients with
acute colitis. Sometimes occurs before onset
of abnormal stools
Appetite
Usually normal or decreased. May be cyclic,
often decreasing in conjunction with flare-ups
symptoms. May be ravenous in some dogs with
inflammatory bowel disease
(especially shar-peis).Appetite may be
increased in cats with inflammatory
bowel disease or lymphoma (transiently
in the latter).
Usually remains normal. May be decreased if
disease is severe (neoplasia, of
histoplasmosis).
Usually occurs as disease becomes more
chronic. Occurs with both malabsorptive and
maldigestive disease processes.
Unusual. May occur in conjunction with
severe colitis, diffuse neoplasia, or
histoplasmosis. If both small and large bowel
signs are present, any weight loss that has
occurred is more likely due to the small
intestinal disease component
Associated signs
Weight loss
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7. Clinical Signs
Small intestine
Large intestine
May be associated with maldigestive or
malabsorptive diseases
Absent
Borborygmus
Maybe present
Absent
Flatulence
Maybe present
Absent
Fecal incontinence
Rare—would only be associated with severe
enteritis and rapid transit of large volumes of
watery diarrhea
May be present
Scooting or
chewing perianal
area
Absent
Occasionally present—may be quite
pronounced in some patients with proctitis
Associated signs
Halitosis
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8. Causes Small Intestinal Diarrhea
• Diet
• Extra-gastrointestinal
diseases
• Infection
• Inflammatory/immune
mediated
• Idiophatic
•
•
•
•
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Neoplasia
Partial obstruction
Motility disorders
Drugs/toxins

9. Causes Large Intestinal Diarrhea
• Diet
• Extra-intestinal
conditions
• Infection
• Inflammatory/immune
mediated
• Idiophatic
•
•
•
•
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Neoplasia
Obstruction
Miscellaneous
Drugs/toxins

10. Small Intestinal Diarrhea
• Diet
– Dietary intolerance [Food hypersensitivity; Food
intolerance; Gluten-sensitive enteropathy]
• Extra-gastrointestinal diseases
– EPI
– Hepatic disease
– Hyperthiroidism
– Hypoadrenocorticism
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11. Small Intestinal Diarrhea
• Infection
– Bacterial [Campyovacter spp; Clostridium spp;
Salmonella spp; E coli; Staphylococcus, SIBO]
– Fungal
– Helminth [Hookworm; Roundworm; Tapeworm;
Whipworm]
– Protozoal [Cryptosporidiosis; Giardia spp]
– Rickettsial
– Viral [Corona virus; Parvovirus; Feline
panleukopenia]
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12. Small Intestinal Diarrhea
• Inflammatory/immune mediated
–
–
–
–
Basenji enteropathy
Duodenal ulceration
Hemorrhagic gastroenteritis
Inflammatory bowel disease [Eosinophilic;
Granulomatous; Lymphoplasmacytic]
– Protein-losing enteropathy and nephropathy of the
Soft-Coated Weaten Terrier
• Idiophatic
– Lymphangiectasia
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13. Large Intestinal Diarrhea
• Diet*
– Dietary hypersensitivity
– Dietary indiscretion
• Extra-intestinal conditions
–
–
–
–
–
Metastatic neoplasia
Neurological disease leading to ulcerative colitis
Pancreatitis
Toxaemia
Uraemia
• Infection
– Bacterial*, e.g. [Campylobacter spp; Clostridium difficile;
Clostridium perfringens; E. coli; Salmonella spp; Yersinia
enterocolitica]
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14. Large Intestinal Diarrhea
• Infection
– Viral* [Coronavirus; Feline immunodeficiency virus
(C); Feline infectious peritonitis (C); Feline leukaemia
virus (C); Parvovirus]
– Fungal, e.g. [ Histoplasmosis; Protothecosis]
– Parasitic*, e.g. [Amoebiasis; Ancylostoma spp;
Balantidium coli; Cryptosporidiosis; Giardia spp;
Heterobilharzia americana; Roundworm; Tapeworm;
Tritrichomonas foetus(C); Uncinaria spp; Whipworm]
– Protozoal, e.g. [Toxoplasmosis]
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15. Large Intestinal Diarrhea
• Immune-mediated/inflammatory disease
– Histiocytic ulcerative colitis of Boxers (D)
– Inflammatory bowel disease*
• Idiopathic conditions
– Fibre-responsive large-bowel diarrhoea
– Irritable bowel syndrome
• Neoplasia*
– Benign, e.g. [Adenomatous polyps; Leiomyoma]
– Malignant, e.g. [Adenocarcinoma; Lymphoma]
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16. Large Intestinal Diarrhea
• Obstruction
– Caecal inversion
– Foreign body*
– Intussusception*
– Neoplasia
– Stricture
• Miscellaneous
– Secondary to chronic small intestinal disease
– Stress
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17. Large Intestinal Diarrhea
• Drugs/toxins
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Acetazolamide
Adder bite
Allopurinol
Aminophylline
Amoxicillin
Amphotericin B
Ampicillin
Atenolol
Benzalkonium chloride
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Bethanechol
Blue-green algae
Borax
Calcium edetate
Carbamate insecticides
Cardiac glycosides
Cephalexin
Chloramphenicol

18. Large Intestinal Diarrhea
• Drugs/toxins
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Chlorphenamine
Colchicine
Cotoneaster
Cyclophosphamide
Cyclosporin
Cytarabine
Daffodil
Diazoxide
Diclofenac sodium
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Dieffenbachia
Doxycycline
Glyphosphate
Honeysuckle
Horse chestnut
Ibuprofen
Indomethacin
Iron/iron salts
Laburnum

19. Large Intestinal Diarrhea
• Drugs/toxins
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Lactulose
Levamisole
Lithium
Loperamide
Mebendazole
Metaldehyde
Methiocarb
Misoprostol
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Mistletoe
Mitotane
Naproxen
Nicotinamide
NPK fertilisers
NSAIDs
Organophosphates
Oxytetracycline

20. Large Intestinal Diarrhea
• Drugs/toxins
– Pamidronate
– Pancreatic enzyme
supplementation
– Paracetamol
– Paraquat
– Pentoxifylline
– Petroleum distillates
– Phenoxy acid herbicides
– Piperazine
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–
–
–
–
–
–
–
–
–
Poinsettia
Procainamide
Pyracantha
Pyrethrin/pyrethroids
Pyridostigmine
Quinidine
Rhododendron
Rowan
Salt

21. Large Intestinal Diarrhea
• Drugs/toxins
– Selective serotonin
reuptake inhibitors
– Sotalol
– Theobromine
– Theophylline
– Vitamin D rodenticides
– Yew
– Zinc sulphate
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22. Thank you…..
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