Application of endoscopic ultrasound to the descending colon and rectum in normal dogs.

Endoscopic ultrasound (EUS) is a medical procedure in which endoscopy is combined with ultrasonography (US) to compensate for problems associated with the transabdominal US such as large penetration depths, presence of intestinal gas, and acoustic shadowing. This prospective, method comparison, pilot study was performed to assess the feasibility of applying EUS in the colorectal region and to describe the typical EUS features of the descending colon and rectum in healthy dogs. Transabdominal US and EUS with or without the hydrosonography were applied to the descending colon and rectum in 10 clinically healthy Beagle dogs and wall thickness, visibility of the wall layers, and conspicuity of the mucosal and serosal surfaces of the intestinal wall were assessed. Endoscopic ultrasound enabled circumferential evaluation of the colorectal wall and provided better visibility of the wall layers and conspicuity of the mucosal and serosal surfaces without degradation of the image, even in the far-field portion of the colorectal wall, compared to US. Moreover, EUS provided the adequate image quality of the rectum, which was difficult to evaluate with US due to deep scan depth and acoustic shadowing by the pelvis. Meanwhile, the application of hydrosonography to EUS deteriorated the visibility of the wall layers and conspicuity of the intestinal wall. The results of this study demonstrate the feasibility of EUS to assess the colorectal region and its potential application for the evaluation of rectal masses or intrapelvic lesions that are inaccessible by the transabdominal US in dogs.

Feasibility of low-dose CT protocols for evaluating the sinonasal cavity and reducing radiation exposure in dogs.

With the increasing use of radiation therapy for treatment of canine sinonasal neoplasia, there is a need for developing low-dose CT protocols to help minimize radiation exposure. The purpose of this study was to assess the trade-off between image quality and reduced radiation exposure of a low-dose CT technique in the canine sinonasal cavity. In this prospective, experimental study, CT images of the sinonasal cavities from 10 normal Beagles were acquired using high-dose (130 kVp) or low-dose (110 kVp, 80 kVp) protocol. Radiation dose and image quality were compared. Radiation exposure measured by the volume-weighted CT dose index and dose-length product was reduced by 36% at 110 kVp and 74% at 80 kVp respectively, compared to the corresponding values at 130 kVp (P = 0.000). Low-dose protocol resulted in higher image noise and reduced signal-to-noise ratio and contrast-to-noise ratio than 130 kVp in most evaluated regions of interest (P < 0.05). CT numbers of the contrast-enhanced structures were highest at 80 kVp (P = 0.000). Conspicuity of most sinonasal structures was similar for high dose and both lower dose protocols. The results of this study indicate that 80 or 110 kVp can be used for sinonasal CT examinations to reduce radiation exposure to the patient without compromising image quality.

Comparison of static-fluid or excretory magnetic resonance urography with computed tomography urography for visualization of nondilated renal pelvises and ureters in healthy Beagles.

OBJECTIVE: To assess the usefulness of magnetic resonance urography (MRU) for the visualization of nondilated renal pelvises and ureters in dogs and to compare our findings for MRU versus CT urography (CTU). ANIMALS: 9 healthy Beagles. PROCEDURES: Dogs underwent CTU, static-fluid MRU, and excretory MRU, with ≥ 7 days between procedures. Contrast medium was administered IV during CTU and excretory MRU, whereas urine in the urinary tract was an intrinsic contrast medium for static-fluid MRU. For each procedure, furosemide (1 mg/kg, IV) was administered, and reconstructed dorsal plane images were acquired 3 minutes (n = 2) and 7 minutes (2) later. Images were scored for visualization of those structures and for image quality, diameters of renal pelvises and ureters were measured, and results were compared across imaging techniques. RESULTS: Excretory MRU and CTU allowed good visualization of the renal pelvises and ureters, whereas static-fluid MRU provided lower visualization of the ureters. Distention of the renal pelvises and ureters was good in excretory MRU and CTU. Distention of the ureters in static-fluid MRU was insufficient compared with that in CTU and excretory MRU. Distinct artifacts were not observed in CTU and excretory MRU images. Static-fluid MRU images had several mild motion artifacts. CLINICAL RELEVANCE: Our findings indicated that excretory MRU with furosemide administration was useful for visualizing nondilated renal pelvises and ureters of dogs in the present study. When performing MRU for the evaluation of dogs without urinary tract dilation, excretory MRU may be more suitable than static-fluid MRU.