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Nephrosplenic Space Ablation

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The Surgical Process: Nephrosplenic Space Ablation

Nephrosplenic space ablation is a hand-assisted laparoscopic procedure that is used to prevent recurrence of large colon entrapment over the nephrosplenic ligament. This ligament connects the left kidney to the spleen. Nephrosplenic entrapment of the colon is a common cause of colic in horses of all ages and breeds. We do not know why the colon should migrate from its normal position on the floor of the abdomen, along the left side of the body wall, and then to settle in a position where it is draped over this ligament. When the colon is entrapped in this position, its contents cannot move through it and the colon becomes distended. This causes the horse considerable pain, and so it displays signs of colic. Diagnosis can be made by palpation per rectum, by ultrasound examination, or at surgery.

Affected horses can be treated by giving them an intravenous injection of a drug, phenylephrine, that shrinks the spleen and makes it easier for the colon to become dislodged when the horse is then jogged. Another treatment involves rolling the horse while it is under a short-acting intravenous anesthetic. These two non-surgical methods work in most cases, although severe hemorrhage is a risk in older horses that receive phenylephrine. A small percentage of horses require surgical correction under general anesthesia through a ventral midline incision. The clinicians treating the horse can inform you as to which of these treatments is indicated in each individual case and will discuss this issue with you before treatment.

(Click to enlarge) Diagram A shows the colon entrapment over the nephrosplenic ligament (NSL) as viewed from the back of the horse. B = after surgery for ablation of the nephrosplenic space with colon in normal position, the X represents sutured area

Although entrapment of the large colon over the nephrosplenic space responds very well to the selected treatment, the condition does tend to recur in a small number of horses. Horses in which the condition recurs are candidates for a hand-assisted laparoscopic ablation or closure of the nephrosplenic space. For this procedure, the horse does not have to be anesthetized, but undergoes a standing surgery with sedation and local anesthesia. A small incision is made in the left flank and the laparoscope is inserted through a smaller incision close by. The nephrosplenic space is then sutured closed so that the trough that forms the space between the kidney and spleen is obliterated and can no longer entrap the colon.

This ablation procedure has a high success rate in preventing recurrence of this particular form of colic. Although the typical candidate for this surgery is one in which the diagnosis of a previous bout of nephrosplenic space entrapment has been made, there are other horses that seem to benefit from the procedure. The latter are horses in which a presumptive diagnosis of nephrosplenic colon entrapment is made. Many of these horses will have recurrent bouts of colic that might resolve with medical treatment at home or after a trailer ride to a veterinary hospital. These horses might also show vague clinical signs, some of which could be mistaken for back pain and other signs of reluctance to work. In such cases, your veterinarian may be able to identify other clinical changes that support the diagnosis of nephrosplenic space entrapment. Surgeons at the University of Florida have considerable experience in performing this surgery and can help identify suitable candidates for the procedure.