Computed tomographic pneumocolonography in normal dogs

Role of CT in the Staging of Colorectal Tumors: A Preliminary Study on 10 Dogs

This study aimed to define the CT features of colorectal tumors in dogs and assess CT's role in tumor staging. It was a retrospective, multicenter, descriptive study involving dogs with a cyto-histopathological diagnosis of colorectal tumors and high-quality pre- and post-contrast CT scans of the abdomen. CT successfully identified colorectal lesions in all cases, showing variations such as wall thickening, presence of masses, and luminal stenosis. It also detected lymph node involvement. Overall, this study helps us to understand the CT features of both epithelial and mesenchymal colorectal tumors, emphasizing CT's importance in staging and surgical planning for affected dogs. Larger studies are needed to identify specific CT findings for different colorectal neoplasms.

Acute hypernatremia and hypocalcemia after oral sodium phosphate administration to a dog

A 15-year-old male neutered mixed breed dog weighing 28 kg presented to a referral center after developing severe tremors and altered mentation. There was hypocalcemia and hypernatremia after oral administration of sodium phosphate as a bowel cleansing agent in preparation for colonoscopy. The dog was treated intravenously with low sodium fluids and calcium gluconate. Neurologic status and electrolyte derangements normalized over the next 12 hours. Oral administration of sodium phosphate appeared to cause clinical electrolyte derangements in this dog.

Evaluation of transanal minimally invasive surgery for submucosal rectal resection in cadaveric canine specimens

OBJECTIVE

To evaluate the feasibility of transanal minimally invasive surgery (TAMIS) for submucosal rectal resection in large breed dogs.

STUDY DESIGN

Cadaveric study.

SAMPLE POPULATION

Canine cadavers (n = 6) weighing between 37.5 and 60 kg.

METHODS

Dogs were positioned in sternal recumbency. After rectal cleansing, a transanal access platform was placed in the rectum, and a pneumorectum was established. An area of ventral rectal wall approximately 2 × 2 cm was resected in a submucosal plane by using laparoscopic instruments and submitted for histopathological evaluation. The rectal wall defect was closed with a single-layer continuous suture pattern with barbed suture. Postoperatively, the rectum was removed en bloc and evaluated for suture or surgical penetration of the serosal surface.

RESULTS

Submucosal rectal resection was successfully completed by using TAMIS in all dogs. The median length of resected specimens after fixation was 24.5 mm (range 9.8-26.5). In two of six dogs, suture was macroscopically visible on the serosal surface, but no dogs had evidence of iatrogenic full-thickness surgical penetration of the rectum. The median distance from the aborad extent of the suture closure line to the anocutaneous junction was 35 mm (range, 35-105).

CONCLUSION

Submucosal resection of the canine rectal wall was feasible in large breed dogs by using TAMIS. No evidence of full-thickness penetration of the rectal wall was seen in these cadaveric specimens.

CLINICAL SIGNIFICANCE

Transanal minimally invasive surgery may provide an alternative minimally invasive approach for resection for benign adenomatous rectal polyps in large breed dogs that might otherwise require a rectal pull-through.

Esophageal insufflation computed tomography in clinically normal dogs

OBJECTIVE To assess the feasibility of esophageal insufflation CT (EICT) for evaluation of the esophagus in dogs. ANIMALS 7 clinically normal adult Beagles. PROCEDURES Each dog was anesthetized twice with 1 week between anesthesia sessions. Dogs were positioned in sternal recumbency during all CT scans. During the first anesthesia session, a CT scan was performed before the esophagus was insufflated (insufflation pressure, 0 mm Hg) and unenhanced and contrast-enhanced EICT scans were performed after CO₂ was insufflated into the esophageal lumen to achieve a pressure of 5 mm Hg. For the contrast-enhanced scan, each dog received iohexol (600 mg/kg, IV), and the scan was performed 30 seconds later. During the second anesthesia session, unenhanced and contrast-enhanced EICT scans were performed in the same manner except the insufflation pressure achieved was 10 mm Hg. The esophageal luminal cross-sectional area and wall thickness were measured at each of 5 segments, and mean values were compared among the 3 insufflation pressures and between unenhanced and contrast-enhanced images. RESULTS Mean esophageal luminal cross-sectional area increased and esophageal wall thickness decreased as insufflation pressure increased. Measurements did not differ significantly between unenhanced and contrast-enhanced images. The stomach became distended with CO₂ at an insufflation pressure of 10 mm Hg but not at 5 mm Hg. No adverse effects were observed. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested EICT was feasible for esophageal evaluation in dogs. Further research is necessary to determine the optimal insufflation pressure for the procedure and its diagnostic efficacy in diseased patients.

Colonoscopic and histologic features of rectal masses in dogs: 82 cases (1995-2012)

OBJECTIVE To evaluate colonoscopic and histologic features of rectal masses in dogs. DESIGN Retrospective case series. ANIMALS 82 client-owned dogs with rectal masses that underwent colonoscopy. PROCEDURES Medical records of dogs with rectal masses that underwent colonoscopy were reviewed. History, signalment, clinical signs, results of physical examination, diagnostic imaging findings, and results of colonoscopy (including complications) were recorded. When available, tissue samples obtained during colonoscopy and by means of surgical biopsy were reviewed by a single board-certified pathologist. Histologic features and tumor grade (when applicable) of tissue samples obtained during colonoscopy versus surgical biopsy were compared. RESULTS Multiple rectal masses were observed during colonoscopy in 6 of the 82 dogs, but no lesions were visualized orad to the colorectal junction. Results of histologic evaluation of surgical biopsy specimens were consistent with a diagnosis of epithelial neoplasia in 58 of 64 dogs, of which 71% were classified as benign adenoma or polyp and 29% were classified as adenocarcinoma in situ or adenocarcinoma. Complications of colonoscopy occurred in 3 of 82 dogs but were considered minor. A discrepancy in diagnosis occurred in 5 of 16 dogs for which both colonoscopic and surgical biopsy samples were available for histologic review. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that multiple rectal masses are uncommon in dogs, and secondary lesions orad to the colorectal junction were not found in this study. Colonoscopy was associated with few complications, but the need for colonoscopic assessment of the entire colon in this patient population may merit reevaluation.

IMAGING DIAGNOSIS - RADIOGRAPHY, ULTRASONOGRAPHY, AND COMPUTED TOMOGRAPHY OF A GIANT FECALOMA CAUSING STERCORAL PERFORATION OF THE COLON IN A DOG WITH A PROSTATIC ABSCESS

A mixed-breed dog presented with tenesmus, hematochezia, and abdominal distension of 2 weeks duration. Radiography showed a large round mass with a "soap-bubble" appearance and shell-like mineralization in the caudal abdomen. Computed tomography revealed a lamellate mineralized mass 8 cm in diameter and containing air in the descending colon and prostatic abscess. Heterogeneously contrast-enhanced, irregularly thickened colonic wall with intramural and peritoneal free gas indicated stercoral colonic perforation. Surgical intervention revealed a tumor-like giant fecaloma in the descending colon adjoining the prostate with extensive wall rupture and fecal peritonitis. Hypothetically, prostatic inflammation may affect colonic motility with resultant fecaloma formation.

Comparison of contrast media for visualization of the colon of healthy dogs during computed tomography and ultrasonography

OBJECTIVE To evaluate contrast agents for their ability to improve visualization of the colon wall and lumen during CT and ultrasonography. ANIMALS 10 healthy adult Beagles. PROCEDURES Food was withheld from dogs for 36 hours, after which dogs consumed 250 mL of polyethylene glycol solution. Dogs were then anesthetized, a contrast agent (tap water, diluted barium, or air; order randomly assigned) was administered rectally, iodine contrast medium (880 mg of I/kg) was administered IV, and CT and ultrasonography of the colon were performed. After a 1-week washout period, this process was repeated with a different contrast agent until all agents had been evaluated. Two investigators reviewed the CT and ultrasonographic images for colon wall thickness, conspicuity, artifacts, wall layering, and degree of lumen dilation at 4 sites. RESULTS Thickness of the colon wall was greatest in CT and ultrasonographic images with water used as contrast agent, followed by barium and then air. The CT images obtained after water administration had a smooth appearance that outlined the colonic mucosa and had the highest score of the 3 contrast agents for wall conspicuity. Although no substantial artifacts related to any of the contrast agents were identified on CT images, barium- and gas-induced shadowing and reverberation artifacts hindered wall evaluation during ultrasonography. For ultrasonography, the degree of conspicuity was highest with barium in the near-field wall and with water in the far-field wall. In contrast to CT, ultrasonography could be used to distinguish wall layering, and the mucosal and muscular layers were distinct with all contrast agents. CONCLUSIONS AND CLINICAL RELEVANCE Use of water as a contrast agent for both CT and ultrasonography of the colon in dogs compensated for each imaging modality's disadvantages and could be beneficial in the diagnosis of colon disease.

Assessment of 3 Bowel Preparation Protocols for Computed Tomography Pneumocolonography in Normal Dogs

OBJECTIVE

To investigate the effects of 3 different bowel preparation protocols on interpretation of computed tomography (CT) pneumocolonography images.

STUDY DESIGN

Experimental crossover design.

ANIMALS

Intact male, hound-cross, research colony dogs (n=4).

METHODS

All dogs received the 3 different bowel preparation protocols for CT pneumocolonography in the same order, with a minimum of 2 weeks between protocols. For each segment of large bowel, the subjective adequacy of bowel cleansing was assessed, residual fecal and bowel volumes were calculated, and the density of fecal material in the bowel lumen was measured. Linear mixed effect models that included a random dog effect were used to evaluate mean differences in outcome measures across protocols.

RESULTS

No dogs experienced any clinical problems associated with the protocols or CT pneumocolonography. Bowel cleansing was considered adequate for CT pneumocolonography interpretation for all 3 protocols. There was a significant effect of protocol on residual fecal volumes and the fecal:bowel volume ratio, with the 2 protocols that included an extended fast producing the lowest total residual fecal volumes. There was a significant effect of protocol on maximum measured density of residual fecal material with the 2 protocols including iodinated contrast having the highest density.

CONCLUSIONS

All protocols were sufficient for CT pneumocolonography interpretation and contrast-tagging of residual fecal material was successful with oral iopamidol administration. An at-home bowel cleansing protocol may provide adequate bowel cleansing for CT pneumocolonography image interpretation.