Cloacal disorders and diseases (Proceedings)
The cloaca is a complex structure in the avian patient. Its primary function is the retention and expulsion of intestinal, reproductive, and urinary products. Due to the complexity of the cloaca and the anatomical structures associated with it, the health of this structure is pertinent to the well being of the avian patient. The anatomy and physiology of the cloaca will be reviewed as well as the diagnosis and treatment of different cloacal conditions. Cloacal disorders discussed will include cloacal infection and inflammation, prolapse, obstruction, and neoplasia. Specific case examples are included for many of these categories.
The cloaca is comprised of three compartments: the proximal coprodeum, the middle urodeum, and the distal proctodeum.1-3 The coprodeum is the connection between the distal colon and the cloaca. The urodeum contains the openings of the ureters and the genital ducts. The coprodeal fold is a sphincter like ridge of tissue that separates the coprodeum from the urodeum. A second ridge within the cloacal lumen called the uroproctodeal fold separates the urodeum the proctodeum. The proctodeum communicates with the outside of the bird's body through the vent. The opening and closing of the vent is controlled by striated sphincter muscle. The Bursa of Fabricius is a diverticulum of the dorsal wall of the proctodeum. The bursa is involved with the immune function of the bird and is the location of B-lymphocyte differentiation. The bursa reaches its largest size at eight to twelve weeks of age and decreases in size as the bird ages.1 In male birds of some species, a copulatory organ may be housed within the cloaca. Anseriformes, ratites and an occasional psittacine species (Vasa parrot, Coracopsis vasa) have phallic bodies housed within the cloaca. The coprourodeal fold prevents fecal contamination of the urodeum and proctodeum, and during defecation protrudes through the vent to serve this function. During the egg laying process the coprourodeal fold will protrude in a similar manner. Most avian species reabsorb water from the urine held in the urodeum. Urine deposited from the ureters into the urodeum often moves retrograde into the rectum where this reabsorption takes place.4-6 Stress-induced polyuria can occur if the bird releases the cloacal contents too quickly for normal urine processing and water reabsorption to occur. The cloacal blood supply is via the pudendal artery and vein. The pudendal nerve provides innervation to the dorsal cloacal wall.
Common Causes of Cloacal DiseaseThe causes of cloacal disease can be related to any of the systems associated with this structure. Causes of cloacal abnormalities include bacterial or fungal infection, inflammation, fecalith or urolith formation, retained eggs, prolapse, or neoplasia. Cloacaliths, with multiple lamellar layers, can develop into large concretions of several centimeters in size causing severe dilatation and obstruction of the cloaca. Masses can develop from the cloacal mucosa or associated structures. Cloacal papillomatosis can produce proliferative lesions of the cloacal mucosa.7-10 This author has had a case of complete cloacal obstruction in an umbrella cockatoo (Cacatua alba) from a fungal granuloma. Cloacal neoplasia is an infrequent diagnosis, but should be included as a differential for a cloacal wall thickening or luminal masses.11 Cloacal lymphoma was diagnosed by the author in an Indian ring-necked parakeet (Psittacula krameri) from cloacal mucosa biopsies obtained via cloacoscopy. Vent stricture and subsequent cloacal obstruction can occur in avian patients secondary to distal cloacal and external vent sphincter abnormalities.
Diagnosis of Cloacal Disease
Diagnosis of cloacal disease is often possible during the initial examination of the bird. A thorough anamnesis should include information on age, gender, reproductive status and activity, diet and management. The avian patient with a blockage of the cloaca will present with clinical signs of obstructive disease. Clinical signs of cloacal disease can vary but include tenesmus, hematochezia, decreased dropping production, diarrhea or change in dropping appearance, flatulence, soiling of vent area, lethargy, anorexia, change in perching posture, inability to breed or produce eggs normally, prolapse of cloacal mucosa or other cloacal structures, or mass effect in the caudal abdominal region.1, 3 If cloacal disease is due to a mass effect within the cloacal lumen, respiratory signs may be apparent due to impingement of the abdominal airsacs. Routine hematology including a complete blood count and chemistry profile will often be normal. Some birds may develop a heterophilic leukocytosis due to secondary bacterial infections or inflammation associated with a cloacitis. A protein electrophoresis may show changes related to inflammation. If cloacal obstruction prevents the normal passing of excrement, congestion of the ureters can occur, causing possible renal failure and hematological changes such as an elevation in uric acid values.12
A thorough cloacal examination should be performed on every bird as part of the routine physical assessment. The vent, or cloacal orifice, should be examined prior to performing an internal cloacal exam. Change in vent size or symmetry, tone or sensation may be present. After the vent has been evaluated, an internal cloacal exam can be performed. A cursory examination can be performed in the restrained bird. A sterile, lubricated, appropriately sized swab should be gently inserted into the cloaca. Intraluminal masses will be detected with this swab technique. The distal cloacal mucosa can then be gently everted for examination. The mucosa should appear moist and pink with a uniform appearance. Any masses or changes in mucosal consistency should be further evaluated. Papillomatosis of the cloaca can cause proliferative mucosal changes.7-10 Application of dilute acetic acid (vinegar solution) to the cloacal mucosa has been reported to increase suspicion of papillomatous changes by causing a white discoloration of the affected mucosal tissue. The definitive diagnosis of papillomatosis is made from histopathologic examination of a biopsy.9,10
Swab samples for bacterial or fungal cultures can be collected. A Gram's stain should be performed on a fecal sample collected from the cloaca. Cloacal cytology can be useful in diagnosing disorders of the lower intestinal tract, reproductive tract, urinary tract or cloaca itself. Cell samples collected from the cloaca may originate from any of these organ systems and additional diagnostics are required to localize abnormalities. Normal cloacal cytology often includes epithelial cells (noncornified squamous or columnar), urate crystals, extracellular bacteria, plant and fecal material and other background debris.13