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.
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.
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.