Nephrectomy should be considered a pragmatic solution for unilateral ureteric trauma, given the certain outcome, if the contralateral kidney and ureter are known to be unaffected. It can also be used to manage unilateral ectopic ureter, even in the absence of hydronephrosis, if ureteric transplantation is impractical, and the contralateral ureter is proven to be normal. For the animal to be a candidate for nephrectomy, contralateral kidney function must be able to provide glomerular filtration rate adequate to sustain life. Another prerequisite is the absence of metastases in cases of neoplasia.
Ideally, individual contribution of each kidney to glomerular filtration rate should be determined before nephrectomy. Since renal scintigraphy is not readily available, intravenous urography may be performed to provide a crude assessment of single kidney function (Figs. 4a and 4b).
Although the following description refers to the removal of a (relatively) normal kidney and ureter, it is important to remember that in many instances the kidney architecture and anatomy will no longer be normal; similarly, neovascularisation may be present.
In those cases the surgeon will have to adapt the technique to the specific circumstances. A surgical assistant is mandatory for this procedure.
The kidney can be approached either via a midline coeliotomy or by incising the flank caudal to the last rib. Although the latter approach allows better access to a single kidney, midline coeliotomy is preferred because it grants better visualisation of the abdominal cavity. This is important in that it helps to allow evaluation of the presence of metastases in cases of neoplasia, and also in order to inspect both ureters and the bladder.
After positioning the animal in dorsal recumbency and preparing the abdomen routinely for aseptic surgery, a ventral midline incision is performed from the xiphisternum to the pubis. The use of an abdominal retractor (such as Balfour, Gosset or Lonestar© depending on the size of the animal) greatly improves the exposure. If not already present, a urethral catheter should be placed before surgery.
The left kidney is visualised by reflecting the mesocolon medially and using it to contain the intestinal loops (Fig. 5), this is called the colonic manoeuvre. The right kidney is exposed by lifting the descending duodenum and using its mesentery to keep the intestines out of the surgical field, the duodenal manoeuvre. The exposed viscera and the margins of the incision are protected by moistened laparotomy swabs.
Figure 5. The left kidney is visualised by reflecting the mesocolon medially and using it to contain the intestinal loops (cranial is to the left of the image and hydronephrosis and hydroureter are present).
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In most instances, the kidney can be removed after capsular stripping: the peritoneum overlying the kidney is lifted and incised with scissors and the kidney is then freed using blunt dissection (Fig. 6). Sharp incision may be necessary if, owing to the disease process, the peritoneum firmly adheres to the kidney capsule. Haemorrhage from capsular vessels is usually minimal and easily controlled with pressure or diathermy. In cases of renal neoplasia, or when the kidney disease has caused dense attachments of the capsule to the parenchyma, the incision is made through the peritoneum to provide a margin around the kidney so that the capsule is removed with the kidney. The assistant supports the kidney during the remainder of the dissection.
Figure 6. The kidney is freed from the overlying peritoneum using blunt dissection. Note the use of a Lonestar© retractor.
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Reflection of the hilar fat, together with gentle medial retraction of the kidney, allows visualisation of the vessels and ureter on the dorsal aspect of the hilus. It is important to identify all extra-renal branches of the renal artery and/or multiple vessels, which are often present, especially in the left kidney. The artery is isolated by careful blunt dissection. Use of right-angled forceps is recommended for this. The artery is double ligated close to the aorta, using synthetic absorbable suture material; for added security against slipping, it is advisable to apply the most distal ligature as transfixing. An excellent alternative is the use of vascular clips. The vein is then ligated in similar fashion.
In intact animals, the left ovarian or testicular vein, which drains into the left renal vein instead of the caudal vena cava, is identified and preserved by ligating the renal vein distal to it. Ligating the renal artery and vein separately prevents formation of an arteriovenous fistula. However, in smaller patients, or if the anatomy is grossly distorted by the disease process, it may be safer to ligate the vessels en masse to minimise the risk of damaging them with consequent haemorrhage. The likelihood of developing an arteriovenous fistula is in fact limited, and there are no cases reported in the veterinary literature.
After vessel transection, the ureter is freed to the level of the bladder with gentle traction (Fig. 7), and ligated close to the trigone using synthetic absorbable suture material. Once resected, the ureter can be pulled free from the retroperitoneal tissue deep to the reproductive tract and removed together with the kidney. Closure of the abdomen is routine.