Biopsy techniques during exploratory laparotomy (Proceedings)

Biopsy and histologic examination should be a part of essentially every exploratory laparotomy in which a direct surgical diagnosis cannot be reached. Relying on gross evaluation and interpretation alone during an exploratory laparotomy will assure that a correct definitive diagnosis will not be reached in some cases. Tissues frequently biopsied at laparotomy include liver, intestine, lymph node, kidney, prostate, stomach, spleen, and pancreas. Less commonly biopsied tissues are urinary bladder and greater omentum.

Liver biopsy

One of the simplest methods to biopsy the liver is the ligature fracture technique. This method is limited in that only the edge of a liver lobe may be sampled, and a surgical assistant is usually needed. A loop of suture material (2-0) is used to strangulate liver tissue proximal to the proposed biopsy site. The tissue is then sharply divided distal to the ligature. The instrument (finger) fragmentation technique is a variation of the ligature fracture technique for obtaining biopsy specimens from the edge of a liver lobe. The proposed biopsy site is isolated from the rest of the lobe by carefully crushing the hepatic parenchyma using either an instrument (e.g., Carmalt forceps) or the thumb and index finger. The parenchyma is fragmented exposing bile ducts and blood vessels to the isolated section. Ligatures of synthetic absorbable material (e.g., polydioxanone) are placed to occlude the vessels and ducts. Division distal to the ligatures completes the biopsy procedure. A wedge resection technique can be used to remove larger biopsy samples. Two rows of overlapping, full-thickness horizontal mattress sutures are placed through the liver. The specimen is excised by sharp dissection distal to the sutures. After any of the above methods, cover the incised edge of liver with greater omentum.

Another versatile method of liver biopsy involves the use of a 4 ti 6 mm skin biopsy puncha. Any portion of the liver may be sampled using this method; however, smaller, partial thickness samples are obtained. The biopsy punch is drilled into the hepatic tissue and twisted to obtain the specimen. Avoid excessively deep penetration into the hepatic tissue so that larger vessels are not traumatized. Hemostasis is achieved by inserting either a topical hemostatic agent (e.g., absorbable gelatin sponge) or omentum into the defect.

Intestinal biopsy

Principles of obtaining intestinal biopsies include the need to obtain multiple biopsies along the length of the intestine, obtain full-thickness samples, and protect the properly closed biopsy site. Technical considerations include size of the biopsy specimen, closure technique, and protection of the incision. Intestinal biopsies are efficiently obtained using a skin biopsy puncha. A 6 mm biopsy punch is usually used in dogs, while a 4 mm biopsy punch may be used in cats. Position the biopsy punch at the antimesenteric aspect and exert rotary forces, taking care to avoid trauma to the opposite (mesenteric) aspect. Close the defect either longitudinally or transversely (the latter is preferred) in a single layer using an appositional, noncrushing suture pattern (e.g., simple interrupted). Synthetic absorbable material is used (e.g. 4-0 polydioxanone). Techniques for visceral wound protection include the use of greater omentum and the use of a serosal patch. Greater omental coverage of the properly closed biopsy site is used when normal wound healing is expected. In cases in which delayed wound healing is possible (e.g., peritonitis or possibly hypoproteinemia), a serosal patch is performed over the biopsy site.

Lymph node biopsy

Abdominal lymph nodes which are frequently sampled include the pyloric (pancreaticoduodenal), colic, and medial iliac (sublumbar) lymph nodes. Excisional or incisional biopsies are preferred to simple aspiration, since morphologic interpretation is possible. Regional blood supply to adjacent tissue should be preserved during incisional lymph node biopsies, especially when sampling mesenteric lymph node(s). For excisional biopsies, divide the blood supply to the lymph node between sutures, and carefully dissect the lymph node from surrounding tissues. Minimally handle the lymph node during excisional biopsy to avoid distorting lymph node architecture.

Kidney biopsy

Kidney biopsies are performed frequently to provide both diagnostic and prognostic information. Kidney biopsy may be accomplished using either a needle biopsy technique or a wedge resection technique. The needleb is inserted through the renal capsule at the caudal aspect of the kidney and is directed within the cortex toward the cranial pole. Digital pressure is then provided to achieve hemostasis at the needle exit site. Biopsy punch (4 mm) or wedge resection biopsies yield larger, more reliable biopsy specimens, yet have a higher risk of hemorrhage during and following biopsy. When using a biopsy punch, obtain a sample of renal cortex using a similar maneuver to that used to obtain a liver biopsy. When using the wedge resection technique, incise the renal capsule, and obtain a wedge-shaped segment of renal cortex using the scalpel blade. The defect is closed using mattress sutures placed through the renal capsule and parenchyma. Greater omentum may also be incorporated in the closure of the renal defect for hemostasis.

Prostatic biopsy

Prostatic biopsies also may be performed at exploratory laparotomy by either needle biopsy or wedge resection techniques. Exposure of the prostate gland is aided by exteriorizing and applying cranial traction on the urinary bladder with a stay suture. Incisional biopsies provide more tissue for study; however, they have more potential for serious complications, such as hemorrhage, infection, and urine leakage, than needle biopsy techniques. The techniques of needle and incisional biopsy of the prostate gland are similar to those for the kidney. Care should be taken to avoid penetrating the prostatic urethra during biopsy. Also, leakage of prostatic contents during biopsy should be minimized.

Gastric biopsy

Gastric biopsies are most often performed in association with gastrotomy. The specimen is obtained by excising an elliptical section of gastric wall from one side of the gastrotomy wound edge. Closure is achieved in two layers using synthetic absorbable sutures.

Splenic biopsy

One technique for splenic biopsy is the wedge resection technique. After placement of a row of overlapping, full-thickness horizontal mattress sutures, the specimen is excised by sharp dissection distal to the sutures. The edges may be oversewn with a simple continuous pattern. Greater omentum also may be incorporated. Alternatively, a biopsy punch may be used to obtain splenic tissue. Larger splenic samples may be obtained by performing a partial splenectomy.

Pancreatic biopsy

A partial pancreatectomy is used to perform a pancreatic biopsy. Careful blunt dissection of pancreatic parenchyma near the end of the lobe of the pancreas exposes pancreatic ducts and blood vessels. These vessels are double ligated with monofilament synthetic absorbable or nonabsorbable sutures and transected.

Biopsy of other tissues

Tissues sampled less commonly at exploratory laparotomy include the urinary bladder and greater omentum. Urinary bladder biopsies are usually taken at the time of cystotomy. An elliptical shaped full-thickness specimen is taken from one edge of the wound margin. Microbiologic sampling of a part of the excised tissue often is indicated. The cystotomy incision is closed in two inverting layers of synthetic absorbable suture material.

Greater omental biopsies are accomplished by excising a section of omentum that has been isolated by sutures. Greater omentum should be preserved whenever possible, because its functions benefit the healing of visceral wounds.

Wound Closure Considerations

The abdominal wall is closed at the completion of the abdominal exploration. The recommended technique for abdominal wall closure has been modified based on biomechanical information concerning healing of abdominal incisions in the dog. Sutures should incorporate the linea alba and external sheath of the rectus abdominis muscle only, being placed approximately 3-10 mm from the wound edge. Closure of a paramedian body wall incision is accomplished by suturing the external sheath only. The extra time and trauma associated with closure of the internal sheath of the rectus abdominis does not yield additional wound strength. The peritoneum is not sutured, as it heals quicker and with fewer complications when not sutured. Sutures are tied only tightly enough to achieve apposition of wound edges. Excessively tight sutures have been shown to yield lower long-term wound strength. Either interrupted or continuous suture patterns using either synthetic absorbable or nonabsorbable suture material is recommended. The simple continuous pattern using nonabsorbable synthetic suture has been shown to be clinically effective. The subcutaneous tissue and skin are closed routinely.

Summary

Biopsy of abdominal tissues is an important part of an exploratory laparotomy when a direct surgical diagnosis cannot be reached. Efficient and effective methods for sampling most abdominal tissues are available. Goals of biopsy include obtaining representative sample(s), maximizing information to the veterinary pathologist, and minimizing patient morbidity.

     a. Baker's biopsy punch, Baker Cummings, Key Pharmaceuticals, Miami, FL 33169.

     b. Tru-Cut® disposable biopsy needle, Travenol Laboratories, Inc., Deerfield, IL 60015.

References

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Dorn AS. Exploratory laparotomy and biopsy techniques. Vet Rec 1986;119: 199.

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