Abdominal Biopsy Techniques
World Small Animal Veterinary Association World Congress Proceedings, 2014
Sara Boyd, BVSC, MMedVet (Surg.)
Johannesburg Specialist Veterinary Centre, Randpark Ridge, South Africa

Introduction

Celiotomy refers to a surgical incision into the abdominal cavity.1 Due to the absence of sophisticated equipment, celiotomy is one of the most commonly used procedures for both therapeutic and diagnostic purposes. The most common approach is via a ventral midline incision; however, paracostal and paralumbar approaches are also possible and are useful for limited exposure of specific organs like the kidneys or adrenal glands.1 Regardless of the reason opening the abdomen, general principles of abdominal surgery should be adhered to whenever an invasive exploratory celiotomy is performed. When a celiotomy is performed for diagnostic procedures, special care must be taken not to create additional problems for the animal like causing haemorrhage or introducing infection into the abdomen.

Liver

The cranial location of the liver may make taking liver biopsies difficult, especially in deep chested dogs. The liver is also an extremely friable organ, especially in the presence of disease. Advanced liver disease may be associated with a decrease in clotting factors which can make intraoperative haemorrhage a risk and require a preoperative whole blood transfusion. Liver disease may also cause hypoalbuminaemia which may cause delayed healing.

The liver consists of 6 relatively distinct lobes which usually have sharp edges and a uniform appearance to the parenchyma. Lobes may become rounded in very young animals or in animals with congested, scarred or infiltrated livers. Where possible, the left side of the liver should be biopsied, especially when using percutaneous techniques, in order to avoid damage to the biliary tree.2,3

Biopsy techniques include percutaneous methods (blind or ultrasound guided), laparoscopy or celiotomy. Percutaneous techniques are not recommended in animals with thrombocytopaenia, cavitatory or highly vascular lesions.3-5 When direct visualization is used, the guillotine method is the most effective way of taking meaningful biopsies. Tru-Cut or skin biopsy punches may also be used and are particularly useful for isolated lesions in the centre of one of the liver lobes.3,4

Stomach

It is advisable to withhold food for at least 8 to 12 hours prior to surgery on the stomach. 18 to 24 hours is recommended for gastroscopic biopsy techniques. In paediatric patients, hypoglycemia is a problem and so starving is only advised for 4 to 6 hours in these patients.6 Surgery of the stomach has relatively little postoperative complications due to the good blood supply and reduced numbers of bacteria.6,7 It also has close proximity to the omental defense mechanisms and rapidly regenerating epithelium. Unless a specific lesion has been identified in the stomach, biopsies should be taken from a hypovascular site along the ventral aspect of the stomach. The pyloric region should be avoided due to the risk of outflow obstruction occurring at a later stage. Biopsy sites should be closed in two layers using a 3/0 or 4/0 absorbable suture material. Gentle pressure is the best way to stop any residual bleeding.

Small Intestine

The small intestine can be biopsied using endoscopic, ultrasonographic, laparoscopy techniques or surgically via a celiotomy. Endoscopic techniques allow good visualization of the mucosa and multiple biopsies can be taken, but biopsies are not full thickness and biopsy of the jejunum is rarely possible.6,7 Celiotomy, on the other hand, allows examination of the entire gastrointestinal tract as well as all other abdominal organs. Multiple, full thickness biopsies are possible, but direct visualization of the mucosa is not.

When performing surgical biopsies of the small intestine, multiple biopsies should be taken. A scalpel, Metzenbaum scissors or a skin biopsy punch can be used. The skin punch biopsies are a very effective technique which provides full thickness, good quality sample and defects that are easy to close. Longitudinal biopsies may be closed in a transverse direction to prevent a decrease in diameter of the intestinal lumen.

Spleen

The spleen is usually biopsied in order to diagnose causes of splenomegaly or infiltrative or neoplastic disease. Percutaneous techniques are effective for the diagnosis of diffuse disease like mastocytosis or lymphoma. Cavitatory lesions should not be attempted using this method, as these may rupture and this could have fatal consequences. When surgery is done, horizontal mattress sutures are used to obtain a wedge or oval shaped biopsy sample.

Pancreas

Pancreatic tissue needs to be handled with extreme care at all times to prevent pancreatitis from occurring. Biopsies are taken more commonly in feline patients as pancreatic disease in this species is more difficult to diagnose than in dogs. Both limbs of the pancreas should be examined and if necessary biopsied. The easiest region to sample is the caudal aspect of the right limb. Samples should be taken from the edge of the pancreas. Tru-Cut tissue core biopsy needles can also be used to gain a suitable sample and this can be done using ultrasound guidance, but direct visualisation is preferred due to proximity of other organs and vasculature.

Colon

Surgery of the colon carries the risk of more complications than does the small intestine, due to the fact that it contains a lot more bacteria and has a poorer blood supply.7 Principles of colonic surgery include causing minimal damage to the blood supply and making sure that each suture is precisely tied and includes the submucosal layer. Surgical sites should be wrapped in omentum prior to closure of the abdomen and surgical sets should also be changed, once the colon is closed, to decrease the chance of abdominal contamination. Where possible, full thickness biopsies should be avoided and for this reason, colonoscopy with multiple mucosal biopsies is the preferred diagnostic technique.

Bladder

Biopsy of the bladder is relatively easy. Stay sutures should be used in the apex of the bladder to make manipulation less traumatic and to minimize spillage. Biopsy samples can be taken from the dorsal or ventral aspect of the bladder. A stab incision is made into the bladder lumen and then slices are taken from the edge of the incision prior to closure. 3/0 or 4/0 absorbable suture material in a continuous pattern is recommended to close the bladder.

Prostate

Occasionally it may be necessary to biopsy the prostate. This is best achieved via a ventral abdominal midline or paramedian incision. A catheter should be preplaced in the urethra, so that this structure is avoided during biopsy taking. A wedge shaped biopsy is removed from the ventrolateral parenchyma and capsule can be over sewn with absorbable suture material to decrease haemorrhage.

Mesenteric Lymph Nodes

Where possible, at least two nodes from the area of interest should be taken. If large enough, Tru-Cut or fine needle aspirate techniques can be used, but wedge biopsies under direct visualisation are preferred. Horizontal mattress sutures can be preplaced through the lymph node and then a 15 scalpel blade used to cut a suitable wedge. Alternatively, perform a complete lymphadenectomy.

Kidney

The kidneys lie in the retroperitoneal space. The right kidney lies at the level of the thirteenth rib whilst the left kidney lies approximately 5 cm caudal to the last rib. Biopsies must always include as much of the renal cortex as possible, as samples containing the renal medulla are seldom diagnostic.5 Biopsy techniques used include: percutaneous methods (of which ultrasound guided techniques are preferred), laparoscopy, surgery or keyhole abdominal surgery techniques. Automated biopsy devices or Tru Cut needles may be used in the latter two techniques. Alternatively wedge biopsies are performed. In this last technique, mattress sutures are placed deep to biopsy site and when tied include a piece of omentum into the incision. This prevents bleeding and helps prevent sutures from pulling out of the very friable kidney capsule.

Adrenal Glands

These glands are usually removed whole when involved in disease processes and seldom if ever are biopsied. Generally surgeons should try and stay outside the capsule of the adrenal glands, especially when neoplasia is suspected, as leaving small pieces behind in the abdomen may lead to tumour seeding. This surgery can be technically difficult due to the fat deposits in this region and vascular structures associated with the glands.

Conclusion

On the whole, biopsy techniques are an extremely useful means of obtaining a definitive diagnosis. As long the basic surgical principles are adhered to, the techniques are safe and the tips provided in this paper should make taking full thickness, good quality biopsies simple and affordable.

References

1.  Fossum TW. Surgery of the abdominal cavity. In: Fossum TW, Dewey CW, eds. Small Animal Surgery. 4th edition. St. Louis, MO: Elsevier Mosby; 2013:356–385.

2.  Radlinsky MG. Surgery of the liver. In: Fossum TW, Dewey CW, eds. Small Animal Surgery. 4th edition. St. Louis, MO: Elsevier Mosby; 2013:584–617.

3.  Cardi M, Mutillo IA, Amaderi L, et al. Superiority of laparoscopy compared to ultrasonography in diagnosis of widespread liver disease. Dig Dis Sci. 1997;42:546.

4.  Cole TL, Centre SA, Flood SN, et al. Diagnostic comparison of needle and wedge biopsy specimens of the liver in dogs and cats. J Am Vet Med Assoc. 2002;220:1483.

5.  Rawlings CA, Howerth EW. Obtaining quality biopsies of the liver and kidney. J Am Vet Med Assoc. 2004;40:352.

6.  Radlinsky MG. Surgery of the digestive system. In: Fossum TW, Dewey CW, eds. Small Animal Surgery. 4th edition. St. Louis, MO: Elsevier Mosby; 2013:339–497.

7.  Tobias KM, Johnston SA. Digestive system. In: Veterinary Surgery Small Animal. Volume 2. St. Louis, MO: Elsevier Saunders; 2012:1425–1690.

  

Speaker Information
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Sara Boyd, BVSC, MMedVet (Surg.)
Johannesburg Specialist Veterinary Centre
Randpark Ridge, South Africa


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