Introduction

Exploratory laparotomy (celiotomy) is one of the most common major soft tissue surgeries performed in general practice. Thorough exploration of the abdominal cavity and its contents requires a surgical approach large enough to allow full evaluation of all the abdominal organs. Thorough exploration also requires a consistent, systematic approach to avoid errors of omission.

Surgical Approach

A ventral midline celiotomy is the usual approach for abdominal exploration. Laparoscopic exploration is also possible. A wide clip and prep is required.

A ventral midline celiotomy from xyphoid to half way between the umbilicus and pubis is usually required for routine exploratory laparotomy. A ventral midline celiotomy from xyphoid to pubis is required if the urinary bladder neck, proximal urethra, prostate in male dogs, inguinal region, or pelvic inlet region requires exposure.

The body wall heals from side-to-side rather than end-to-end. Do not be afraid to open the abdomen from stem to stern. An inadequate length of incision in the body wall can result in iatrogenic damage to intraabdominal structures by excessive traction, rupture of hollow organs or abscesses in attempting to exteriorize them through a small opening, or failure to identify significant lesions through inadequate exposure.

A self-retaining abdominal retractor (Gossett or Balfour) is extremely useful. Protect the edges of the abdominal wall with moistened laparotomy sponges, moistened gauze swabs, or moistened hand towels. A 'sponge count' before opening and closing the abdomen is best practice.

In the male dog, the skin incision caudal to the umbilicus should be made paramedian. I find dogs more comfortable after surgery if the skin incision is swung lateral at the level of the umbilicus and progresses caudally lateral to the caudal-most nipple and medial to the second most caudal nipple. The subcutaneous tissue is dissected to allow incision on the midline of the body wall. The caudal part of the incision usually requires 2 layers of subcutaneous sutures except in very thin animals.

Exploratory Technique

On opening the abdomen, check for the presence of free fluid. A small amount of clear, colorless abdominal fluid is normally present in young puppies and kittens. A sample should be obtained of any other fluid present by aspiration with a syringe. Small volumes of fluid are most apparent in the paralumbar fossae (so-called gutters).

Two general techniques for abdominal exploration are available. Some surgeons prefer to divide the abdomen in quadrants and explore each quadrant in turn. My preference is to explore generally from cranial to caudal beginning with the alimentary system and followed by the endocrine and genitourinary system. A suggested exploratory technique follows.

1.  Examine the peritoneal surfaces of the lateral abdominal walls and diaphragm.

2.  Observe the liver for colour, size, and sharpness of its edges.

3.  Examine the ventral surface of all liver lobes, the dorsal surface of all liver lobes, and palpate all liver lobes.

4.  Examine the gallbladder and extrahepatic biliary tree. Do not express the gallbladder until after the intestinal tract has been examined.

5.  Examine the stomach beginning at the esophagus and progressing to the pylorus. Palpate the stomach for any foreign material in the lumen and for abnormalities of the gastric wall (thickened areas, fibrotic areas, etc).

6.  Examine the spleen and omentum. Exteriorize the spleen to examine both surfaces.

7.  Examine the hepatic lymph node just distal to the pylorus.

8.  Examine the duodenum from the pylorus to the duodenocolic ligament.

9.  Examine the left limb of the pancreas in the mesoduodenum. Examine the head of the pancreas. In some animals, the right limb of the pancreas can be visualized at this point, but it is often more easily identified later.

10.  Examine the portal vein (ventral to and smaller than the caudal vena cava) in the ventral mesoduodenum and its associated lymph nodes.

At the duodenocolic ligament, some people prefer to carry on examining the small intestine and others prefer to go to the colon and work backwards. My preference is to carry on from cranial to caudal, but it doesn't matter as long as the entire small and large intestine is examined.

1.  Examine the jejunum, running the jejunal wall between your fingers and at the same time examining the mesojejunum and mesenteric lymph nodes.

2.  Continue in a similar fashion to examine the ileum, which can be identified by its antimesenteric longitudinal vessel.

3.  Examine the cecum and ileocecocolic junction and its associated lymph node. Examine the ascending, transverse, and descending colon along with the mesocolon and associated lymph nodes.

4.  Using the mesocolon as a physiologic retractor to hold back the intestines, examine the left kidney, left ureter, left adrenal gland (readily identified with the phrenicoabdominal vein crossing its ventral surface just cranial to the kidney), and left ovary and uterine horn (in females).

5.  Using the mesoduodenum as a physiologic retractor to hold back the intestines, examine the right kidney, right ureter, right adrenal gland (usually difficult to identify and often lying beneath the caudal vena cava), right ovary and uterine horn.

6.  Examine the urinary bladder and proximal urethra. In the male, examine the prostate and visualize the vas deferensi entering the prostatic urethra by retroflexing the urinary bladder (this is the easiest way to look for a cryptorchid testicle--find the vas deferens and follow it proximally).

7.  With the urinary bladder retroflexed, palpate immediately caudal to the bifurcation of the aorta for sublumbar lymph nodes. In normal animals, the small size of the lymph nodes and fat in the area makes them difficult to see or feel.

8.  Finally, go back and gently express the gallbladder.

Biopsy Techniques

Liver Biopsy

Can be accomplished by:

 Strangulating suture technique for diffuse lesions or marginal masses using monofilament absorbable suture on a taper needle. Use natural lobular cleavage planes when possible. Use a modified transfixation ligature crushing through the liver parenchyma with the suture material. Excise the biopsy distal to the ligature, trying to avoid handling the liver with forceps (you can allow it to drop onto a gauze sponge). Check for hemorrhage. If bleeding, use a fine gauge 'tissue ligature' to compress the hepatic parenchyma.

 Partial lobectomy by finger-fracture technique. Use fingers to crush through hepatic parenchyma sparing the small blood vessels and bile ducts. Individually ligate vessels and ducts.

 Baker's biopsy punch (skin biopsy punch) is useful for lesions away from the periphery. Use the biopsy punch similarly to its use for a skin biopsy. Gelatin foam hemostatic agent can be used to pack the hole for hemostasis.

 Since the abdomen is open, fine needle aspiration and Tru-Cut needle biopsies should be avoided in favour of giving your pathologist more tissue to work with.

Stomach Biopsy

This is obtained in a similar fashion to a gastrotomy incision. Use stay sutures to elevate the stomach out of the abdomen and pack off the area with moistened laparotomy sponges or swabs. Make a full-thickness stab incision with a scalpel and extend with scissors. Excise a crescent of full-thickness crescent from one side of the gastrotomy incision. Any method of closure is acceptable. I prefer a simple continuous monofilament absorbable in the mucosa and a second line of simple continuous in the seromuscularis.

Small Intestinal Biopsy

For suspected IBD or other diffuse mural infiltrative disease, biopsy of all 3 areas of the small intestine (duodenum, jejunum, ileum) is recommended. Exteriorize the affected segment of intestine. Occlude the lumen with assistant's fingers or atraumatic intestinal forceps (Doyen). Make a stab incision in the antimesenteric border of the intestine and extend with scissors for 1 cm parallel to the long axis of the intestine. Excise a full-thickness crescent of intestine from one side of the enterotomy. Close in the same direction as the incision was made using full-thickness simple interrupted appositional sutures (or full-thickness simple continuous appositional sutures) of 3-0 or 4-0 monofilament absorbable suture on a taper needle. For all small intestinal closures, the suture bites should be 2-3 mm from the cut edge and 2-3 mm apart. Put each specimen in a separate contained or onto a biopsy cassette labelled appropriately.

Pancreas Biopsy

The pancreas must be handled gently. For most biopsy procedures, interlobular dissection with a fine, curved, mosquito hemostatic forceps is recommended. Avoid electrocautery. Use 4-0 monofilament absorbable suture to ligate small blood vessels and ducts. Be careful to avoid damaging the blood supply to the duodenum. Be sure to close any defect in the mesoduodenum.

Mesenteric Lymph Node Biopsy

Either incisional or excisional biopsy can be used for mesenteric lymph nodes. Avoid lymph nodes directly overlying the cranial mesenteric artery and vein, especially in cats, as these vessels can be easily traumatized and can lead to complete devascularisation of the small intestine. Use a fine, curved mosquito haemostat to establish a dissection plane. A superficial slice of the lymph node can be accomplished. Close the mesentery.

Adrenal gland biopsy is rarely indicated. Exposure can be difficult and hemorrhage can be a serious problem.

Splenic Biopsy

Mass lesions of the spleen are usually managed by splenectomy. Partial splenectomy by hilar ligation of blood vessels and gentle oversewing of the cut edge of the spleen with fine, absorbable suture material is occasionally indicated. Parenchymal lesions can be biopsied in similar fashion to the liver.

Colonic Biopsy

Full-thickness colonic biopsies are rarely indicated. Mucosal biopsies obtained by colonoscopy are usually adequate for diagnosis of colitis. If full-thickness biopsy is required, a technique similar to the small intestine can be used. Extra care is required to prevent contamination of the peritoneal cavity with colonic contents.

Kidney Biopsy

Is most often performed by Tru-Cut needle biopsy. Temporary vascular occlusion and nephrotomy or partial nephrectomy are occasionally required.

Urinary Bladder Biopsy

This is most often obtained by catheterization if open biopsy of a suspected TCC is contraindicated due to the potential for seeding the abdomen and the abdominal wall with tumour cells. If TCC is suspected, careful imaging of the urinary system should be completed before surgery. Full-thickness bladder wall biopsy is often obtained at the time of cystotomy for removal of stones and/or for suspected feline interstitial cystitis. A full thickness stab incision in the bladder and excision of a strip of wall is performed. The bladder can be closed with fine (4-0) monofilament absorbable suture in a simple continuous pattern.

Prostate Biopsy

The prostate can be biopsied by fine needle aspiration, Tru-Cut needle biopsy, or incisional biopsy. For incisional biopsy, placement of a urethral catheter to avoid entry into the urethral lumen is useful. Make a stab incision in one lobe of the prostate and excise a piece of wall. Close the prostate with absorbable sutures of omentalize it.

General Comment

If the animal's clinical condition has warranted an exploratory and no gross lesions are found, biopsy, biopsy, biopsy! If it has been worth putting the animal through a general anaesthetic and surgery, it is worth getting appropriate samples to reach a diagnosis. Anything that has been removed should be sent for histopathology. Tissue samples for culture may be warranted in some cases.