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12-year-old, male castrated, Cocker Spaniel presented with hemorrhagic diarrhea and tenesmus for 2–3-week duration.

Photograph of the dog’s perineum is provided below.

Ultrasound videos concentrating on the colon are provided below.

 

Photograph of the dog's perineum

Ultrasound video clip of the colon, both transverse and sagittal

The descending colon has an intussusception that courses past the pelvic canal. The intussusceptum is small and surrounded by moderately hyperechoic mesentery. The intussuscipiens has moderately diffusely thick wall.  Luminal colonic  contents orad to the intussusception is strongly shadowing.

Other findings not provided in images above:

Liver is mildly diffusely enlarged, and contains few, small, hypoechoic nodules that do not bulge the margins. Gallbladder contains a small to medium amount of hyperechoic material. Body of the spleen contains a small (2.1 cm), well marginated, round, heterogenous, mainly hyperechoic mass that mildly bulge the margins. Pancreas is moderately diffusely enlarged and moderately irregularly marginated. Other organs were unremarkable.

Diagnosis:

1. Colonic intussusception

2. Small splenic mass

3. Moderate, diffuse pancreatopathy

4. Mild, diffuse hepatomegaly and nodular hepatopathy

5. Mild cholestasis

Dog transferred to AMC for evaluation of intussusception. At presentation, patient was alert, responsive, tachycardic, mildly hypertensive, 5 % dehydrated, moderately tense on abdominal palpation with an approximately 2 cm colonic prolapse. Prolapse was painful, discolored and diarrhea exuded from lumen. Packed cell volume 35%, total solids 9.0 and blood gas analysis revealed mild metabolic acidosis.

Due to inherent limitations of the modality, the ultrasound did not determine the true extent of the intussusception and its relation to the rectal prolapse.  The ultrasound also did not have information regarding vascular integrity of the colon walls. Computed Tomography was recommended for further evaluation prior to surgery (see below).

 

Sagittal image for localizer; transverse CT images of the abdomen, venous phase post-contrast

Para-sagital CT images of the abdomen, venous phase, post-contrast

A colonic- colonic intussusception is noted, beginning cranially at the level of the ileocolic junction. The beginning of the ascending colon becomes the intussusceptum just caudal to the ileocolic junction at the level of the left kidney. The intussusceptum spans the entirety of the dilated intussusceptien, extending to the pelvic inlet and perineum. The normally contrast enhancing wall of the intussusceptum becomes lost, particularly the left lateral wall, as it extends to the rectum. For approximately 2.7 cm length, the caudal most aspect of the colonic intussusceptum is prolapsed from the rectum, exposed to surrounding air and has complete loss of normal wall layering. Arterial phase (not shown) did not identify any loss of arterial supply to the colon. A hypo-attenuating liver nodule is most visible on the first two venous phases but becomes iso-attenuating to the regional normal liver on the last venous phase. A mildly capsule deforming splenic nodule remains heterogenous in the head of the spleen.

Diagnosis

1. Colonic-colonic intussusception, to include prolapse of part of the intussusceptum through the rectum.

2. Suspect vascular compromise/necrosis to the prolapsed portion of the intussusceptum.

3. Mild ileocolic lymphadenopathy.

4. Nonspecific hypoattenuating and capsule deforming nodule of the spleen and liver.

 

The colonic-colonic intussusception extended caudally through the pelvic inlet and is involved in the prolapse. There is loss of mucosal contrast enhancement and wall layering of the colon caudal to the pelvic inlet (suggesting vascular compromise), but mucosal enhancement of colon in the abdomen remained intact. Surgical intervention is recommended.

The loss of enhancement pattern on later imaging of the liver nodule suggests benign etiologies. The splenic nodule is non-specific, perhaps related to benign etiologies though malignancy cannot be ruled out.

None of the walls associated with the intussusception have evidence of mass. However, neoplasia as a reason for the intussusception cannot be ruled out.

Outcome:

Abdominal laparotomy revealed the intussusception was mostly viable. Intussusception extended from the transverse colon through the pelvic canal with necrotic tissue exuding from the rectum. Prolapse was partially reduced per rectum, resection and end-to-end anastomosis of the colon was performed, removing approximately 5 cm of affected tissue. Splenectomy, subcutaneous mass removal and liver biopsy performed.

– Spleen Histopathology: Splenic nodular hyperplasia

– Resected Descending Colon Histopathology: Gastrointestinal stromal tumor vs Leiomyosarcoma: Immunohistochemistry: PENDING

– Liver Biopsy: Nodular hyperplasia with vacuolar degeneration

 

Transverse CT images (post-contrast). White arrows denote the abrupt loss of wall enhancement of the intussusceptum, consistent with necrosis.

Transverse CT image (post-contrast), further cranially than the prior image. Note the normal circumferential enhancement to the wall of the intussusceptum.

Photograph of intra-abdominal surgery denoting the cranial extent of the intussusception.

Discussion:

Abdominal ultrasonographic findings that have been reported for intussusceptions include target-like mass with multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center on transverse images. Longitudinal sections consists of hyperechoic and hypoechoic parallel lines. The most common form of intussusception in dogs is at the ileocolic junction. Common causes include foreign bodies, parasitism, intestinal masses, viral enteritis and previous intestinal surgery.

With abdominal ultrasound, Patsikas 2005, reported that if color doppler indicated blood flow within mesenteric vessels of intussuscepted intestine, surgical reducibility of affected tissue was possible in 75% of dogs. Venous blood flow may be more diagnostic when determining reducibility since congestion of venous vessels leads to edematous congestion of the serosal layer causing fibrous adhesions. As a result, reducibility is less likely.

With Computed Tomography, Tsuka et al 2020, reports the advantages of CT as follows: able to distinguish layers of intestinal wall with a gas filled lumen, allows pursuit of proximal to distal course of intestine to estimate size/region or origin, and contrast enhancement can differentiate intraluminal hemorrhage, inflammation, neoplasia or mesenteric ischemia in human medicine. Lee et al. 2009, described that the evaluation of intestinal wall contrast enhancement was also possible in the intestinal and venous phase technique which may be useful in the evaluation of mesenteric circulation in dogs. Barge et al 2020. described a dog with poor enhancement of the colonic wall, had extensive necrosis at the time of surgery.

Colonic-colonicc intussusceptions are not commonly reported in dogs. The chronicity of disease as well as appearance of prolapsed intussusceptum at presentation led to concern of the colonic viability. Multiphasic contrast-enhancement CT was able to determine the viability, origin, and extent of the affected area as well as guide surgical intervention.

Neither CT nor surgical evaluation of the non-viable portion of the colon suggested an underlying neoplastic process. However, considering the presentation of this intussusception in an older dog, neoplasia as a cause of the intussusception could not be ruled out.

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