Читать книгу Small Animal Surgical Emergencies - Группа авторов - Страница 176

Laboratory abnormalities depend on the type and extent of obstruction, as well as the duration and severity of clinical signs. Many of the clinicopathologic abnormalities result from dehydration and hypovolemia that accompany the obstruction. Dehydration may result in an elevated hematocrit, total protein, and urine specific gravity, as well as prerenal azotemia. Hypoproteinemia and hypoalbuminemia may occur in animals with GI perforation‐induced septic peritonitis or in those with chronic obstructions marked by long‐standing protein‐losing diarrhea. Elevations in hepatic enzymes, particularly alanine transaminase, may be seen as a consequence of hypovolemic shock and reduced hepatic perfusion. Preoperative hypoalbuminemia has sometimes been associated with postoperative dehiscence of anastomotic sites or mortality [23,27–31], but in other studies hypoalbuminemia had not increased these risks [32–34]. Toxic effects of some foreign bodies, such as those composed of zinc or lead, may precipitate toxin‐specific laboratory abnormalities.

Acid–base abnormalities are common in animals with foreign body obstruction. In a study of animals by Boag et al. [4], it was found that 74.6% had elevated bicarbonate, 51% had hypochloremia, 45.2% had metabolic alkalosis (base excess greater than reference range), and 40–45% had hyperlactatemia. There was no statistical association between biochemical abnormalities and location of the foreign body at surgery (proximal or distal to the duodenal papilla). Hypochloremic, hypokalemic metabolic alkalosis was identified in 12% of dogs with proximal GI obstructions and 13.7% of dogs with distal GI obstruction [4].

Biochemical evaluation of abdominal fluid can be an aid to identifying the presence of foreign body‐induced septic peritonitis. A blood to fluid glucose difference of greater than 20 mg/dl was 100% sensitive and 100% specific for the diagnosis of septic peritoneal effusion in dogs and 86% sensitive and 100% specific in cats. A blood to fluid lactate difference of 2.0 mmol/l or less was also 100% sensitive and 100% specific for the diagnosis of septic peritoneal effusion in dogs [35]. Use of a veterinary handheld glucometer results in a high incidence of false negatives in identification of septic peritonitis because the relatively low cellularity of peritoneal effusion falsely elevates fluid glucose compared with blood glucose, thus reducing the ratio between samples [36].