T Mannucci

Peripheral nerve stimulation under ultrasonographic control to determine the needle-to-nerve relationship

OBJECTIVE To determine the needle-to-nerve distances during electrical nerve location in dogs at different currents and pulse duration using a peripheral nerve stimulator (PNS) under ultrasound control (US), and the minimal electrical thresholds (MET) necessary to obtain a motor response (MR) after achieving needle-to-nerve contact. STUDY DESIGN Prospective in vivo experimental trial in a clinical setting ANIMALS Thirty dogs, scheduled for locoregional anaesthesia of the sciatic nerve. METHODS Needle-to-nerve distance was measured ultrasonographically after obtaining the MR of sciatic nerve with 2, 1 and 0.5 mA and pulse duration 0.1 ms (NS0.1). Thereafter the needle was placed in contact with the nerve and MET was determined. The procedure was repeated with 0.3 ms (NS0.3). Finally the needle was reintroduced to contact the sciatic nerve guided only by US, thus MET-US was determined. Data were analysed using Kruskal-Wallis or Mann-Whitney tests. RESULTS Needle-to-nerve distances were greater when MR was obtained with 2 mA than with 1 and 0.5 mA at 0.1 and 0.3 ms. No significant differences were observed between the needle-to-nerve distances using 0.1 or 0.3 ms. The MET [median (range)] was 0.4 (0.18-1.3) mA in NS0.1, 0.32 (0.12-0.8) mA in NS0.3; while MET-US was 0.7 (0.32-1.5) mA. When the needle contacted the nerve, the MR achieved with currents below 0.3 mA was obtained in 17.2, 40 and 0% of cases using NS0.1, NS0.3 and US respectively. CONCLUSIONS AND CLINICAL RELEVANCE The electrical current necessary to obtain a MR decreased as the needle moved towards the nerve. However when the needle tip contacted the nerve, an MR with low current intensity could not be obtained. Thus the absence of motor response at currents below 0.3 mA cannot rule out needle-epineurium contact. When ultrasound is combined with PNS, it is more important to assess the correct needle position than searching for an MR at low currents.

MICRONODULAR ULTRASOUND LESIONS IN THE COLONIC SUBMUCOSA OF 42 DOGS AND 14 CATS

Micronodular ultrasound lesions have been detected in the colonic submucosa of dogs and cats at our hospital. The lesions had rounded/oval shapes, measured 1-3 mm in size, and exhibited a hypo/anechoic ultrasonographic pattern. To our knowledge, these lesions have not been previously reported in human or veterinary patients. The purpose of this retrospective study was to determine whether micronodular lesions were associated with other abdominal ultrasound abnormalities or clinical findings. Medical records of dogs and cats with sonographic reports describing micronodular lesions within the colonic submucosa were reviewed. Concurrent ultrasonographic abnormalities were recorded and compared with clinical sidgns and follow-up data. A total of 42 dogs and 14 cats met inclusion criteria. Concurrent sonographic abnormalities included the following: increased colon wall thickness (12.5%); small bowel wall thickening, altered layering, and/or hyperechoic mucosa (45%); abdominal effusion (29%); caudal mesenteric lymphadenopathy (46%); mesenteric lymphadenopathy (27%); and pericolic peritoneal fat reactivity (9%). Fifty of 56 animals presented with diarrhea. Twenty-seven cases had clinical signs of colitis and ultrasonographic lesions were limited to the colonic submucosa. In nine cases, follow-up examination at 6-8 weeks showed resolution of clinical and ultrasonographic signs. Ultrasonographic and clinical examinations in 17 patients at 12-18 months and in 20 patients at 18-30 months from initial diagnosis showed resolution of submucosal lesions and clinical signs of enteropathy. The authors propose that micronodular submucosal ultrasound lesions may represent reactive intraparietal lymphoid follicles and may be indicators of colonic inflammatory diseases in dogs and cats.