LAPAROSCOPIC ANATOMY OF THE ABDOMEN IN DORSALLY RECUMBENT HORSES

Objectives-To provide an accurate and detailed description of the lapa roscopic anatomy of the abdomen of horses positioned in dorsal recumbe ncy and to compare those observations with laparoscopic anatomy of sta nding horses. The effects of laparoscopy and positional changes on art erial blood pressure and blood gas values also were investigated. Desi gn-Descriptive anatomic study. Sample Population-Laparoscopy was perfo rmed on 6 horses (2 mares, 2 geldings, and 2 stallions) to record the normal laparoscopic anatomy of the abdomen in dor sai recumbency. Proc edure-Feed was withheld from all horses for 36 hours. Horses, under ge neral anesthesia, were examined in horizontal and inclined positions ( head-up and head-down). Intermittent positive-pressure ventilation was used, arterial blood pressure was continuously monitored, and samples for arterial blood gas measurements were taken at intervals. Results- The main structures of diagnostic relevance observed in the caudal reg ion of the abdomen were the urinary bladder, mesorchium and ductus def erens (left and right), left and right vaginal rings, insertion of the prepubic tendon, random segments of jejunum and descending colon, pel vic flexure of the ascending colon, body of the cecum, and cecocolic f old. The main structures observed in the cranial region of the abdomen were ventral surface of the diaphragm, falciform ligament and round l igaments of the liver, ventral portion of the left lateral, left media l, quadrate, and right lateral lobes of the liver, spleen, right and l eft ventral colons, sternal flexure of the ascending colon, apex of th e cecum, and stomach. Conclusions-Alterations in cardiovascular and re spiratory function in response to pneumoperitoneum and various positio nal changes indicated the need far continuous and throrough anesthetic monitoring and support. Comparison of anatomic observations made in d orsally recumbent, inclined horses with those reported for standing ho rses should enable practitioners to make patient positioning decisions that best suit access to specific visceral structures. Development of special instrumentation for manipulation of the viscera in horses, pa rticularly the intestinal tract, would increase the diagnostic and the rapeutic capabilities of laparoscopy during dorsal recumbency.