Ancillary gastrointestinal diagnostics in camelids (Proceedings)

First compartment fluid examination

First compartment (C1) fluid examination is a diagnostic aid for animals exhibiting abdominal distension, reduced fecal output, anorexia, and abnormal first compartment texture or motility.

C1 fluid may be obtained by passage of an orogastric tube with aspiration by a dosing syringe or reversed stomach pump. The use of a weighted tube allows passage of the tube ventrally to maximize fluid obtained. This method may result in salivary contamination, which significantly affects some analytes, including pH, Na, K and methylene blue reduction time (in cattle)

First-compartment paracentesis completely avoids salivary contamination and is therefore the preferred method for pH determination. It usually results in a smaller sample volume and carries a low risk of subcutaneous abscessation and localized peritonitis. It should also be avoided in females in late gestation.

To obtain fluid in adult llamas, the site for insertion is 20cm caudal to the last costochondral junction. This endpoint should be clipped and disinfected and the animal should be well-restrained. A 16ga, 2-3" needle should then be directed dorsomedially and thrust into the first compartment. About 4-5 mL can usually be obtained by this method.

Once collected, the fluid should be placed in a clean vial and either analyzed immediately or kept at body temperature until timely analysis can be performed.

Table 1: First Compartment Fluid Reference Ranges in Llamas (Adapted)3

C1 fluid pH is best measured using a pH meter, as they are less affected by the color of the fluid, as are pH papers. A drop of fluid may be placed on a warm glass slide and examined using a microscope. On low power, numerous protozoa should be seen moving rapidly across the slide. Three sizes of protozoa should also be identified, small, medium and large. The large protozoa are the most sensitive to lactic acidosis and will be the first to be lost in cases of rumen acidosis. This slide may then be dried and Gram stained to assess ratios of G pos and G neg bacteria.

Methylene blue reduction time is determined by mixing 1 drop of 0.03% methylene blue to 20 drops of fresh fluid in a clear tube. The time taken for the C1 fluid to be decolorized back to its original color is then determined, which is the result of normal anaerobes reducing the methylene blue. Sedimentation time is determined by placing C1 fluid into a clear tube and watching for feed particles to sink to the bottom of the tube. With active fermentation, gas bubbles cause the feed to float. Samples that sediment quickly have inadequate fermentation.

C1 fluid chloride concentration is a useful test that may be submitted to a laboratory and run as a "urine" chemistry. Laboratories should be asked to specifically run a coulometric titration to determine chloride concentration, over potentiometric determination, which has been shown to overestimate chloride concentrations in rumen fluid.

C3 HCl reflux into C1 occurs due to vagal-type indigestion, small intestinal obstruction or ileus. Because of highly effective C1 buffering systems and volume, this HCl will not cause the C1 pH to change, but will alter [Cl-]. C1 [Cl-] should be interpreted carefully in animals that have received oral electrolytes.

Abdominocentesis

Abdominocentesis can be quite useful in determining the presence of specific conditions, such as uroabdomen and hemoabdomen, and for differentiating between inflammatory and non-inflammatory conditions of the abdomen.

If ultrasound is available, it is most appropriate to perform centesis in an area confirmed to have excess fluid. It is preferable to have animals standing, but sternal recumbency is also acceptable. If ultrasound is not available, a blind tap may be performed in the right paracostal area, 1-2 cm dorsal and 3-5 cm caudal to the costochondral junction of the 12th rib Alternatively, the ventral midline on the linea alba at the umbilical site may be sampled. The selected site should be clipped, aseptically prepped and an 18ga, 1.5-2" needle introduced perpendicular to the body wall. When ultrasound is not available, it is preferable to use a teat cannula after desensitizing the skin and body wall with 2% lidocaine, making a skin stab incision and introducing the cannula through the body wall. If a cannula is used, it should be wrapped in gauze to prevent contamination by skin bleeding.

For cytology, the sample should be placed in a tube containing EDTA, while culture samples should be in plain sterile tubes. If the volume obtained will not fill the EDTA tube at least ¼ full, the EDTA tube should be shaken out prior to introducing fluid, as EDTA increases the refractive index of fluids. Samples should then have TP determined on a refractometer and air-dried smears made immediately.

Values for normal abdominal fluid in ruminants and pseudoruminants often overlaps with those associated with pathologic conditions. Therefore, fluid must be interpreted in light of all available information for the case. Abdominal fluid changes composition are known to change during the periparturient and post-operative periods in cattle, which is likely true in camelids.

Table 2: Selected Peritoneal Fluid Reference Ranges for Llamas and Alpacas (Adapted)

Fluid of abnormal character or volume may be classified into one of 3 categories. Transudates have a total protein (TP) of <2.5g/dL and a TNCC of <5000/uL. Transudates may occur with heart failure conditions, chronic renal failure, parasitism, starvation, maldigestive or malabsorptive disorders or ruptured urinary bladder.

Modified transudates have a TP of 2.5-3g/dL and a TNCC of 5,000-10,000/uL. This fluid may be produced in some normal animals, from portal hypertension from hepatic lipidosis, congestive heart failure, or urinary bladder rupture.

Exudates possess a TP of >3g/dL and a TNCC >10,000/uL. When degenerate neutrophils compose >80% of the TNCC, septic peritonitis secondary to surgery, vaginal perforation, GI perforation, liver or umbilical abscesses, pyelonephritis or trauma should be considered. Other WBC types may predominate during chronic septic, protozoal, fungal, hypersensitivity or foreign body-induced peritonitis.

Currently, efforts are being made to more accurately classify fluids by their pathophysiology, rather than simply their protein and cellular components. Terminologies for this classification system include protein-rich and protein-poor transudates, exudates, hemorrhagic, lymphocyte-rich effusion and uroperitoneum.

Liver biopsy

Biopsy of the liver serves to diagnose both individual and herd-level diseases, including trace mineral deficiencies, toxic, infectious and metabolic diseases.

As with abdominocentesis, it is preferable to do liver biopsy under ultrasound guidance, allowing for avoidance of major vessels and for measurement of minimum and maximum depths to target the liver. The liver is imaged over the right cranial abdominal wall, and may be seen in the last few intercostal spaces, extending to just beyond the last rib. In general, the intersection of a line from the tuber coxae to the elbow on the right side and the 10th intercostal space is a good starting point. The area should be clipped, prepared and desensitized with 2-3mL of 2% lidocaine. The instrument chosen should be inserted through a stab incision and directed toward the opposite elbow, and the sampling chamber opened and closed. The sample should then be placed in an evacuated tube and chilled for mineral analysis or culture, or placed in formalin for histopathology. Standard rubber top tubes should be avoided for Zn testing; royal blue top tubes have rubber stoppers which do not contain zinc. Samples for mineral analysis may also be frozen until analysis.

Instruments used for liver biopsy include manual and automatic Tru-Cut instruments (Bard Medical, Covington VA 30014). When used for liver sampling, it is recommended that 16 or 14ga instruments be selected. While these instruments provide good samples for histopathology and culture, they do not typically provide enough tissue for mineral analysis. At least three samples may be required per animal to provide a sufficient tissue mass for mineral panels.

Liver is the tissue which best represents the trace mineral status of animals. This is particularly true for Cu, Se, Zn, Fe, P, Co, for which liver is the primary pool or blood levels may be altered by various pathologic and physiologic states, including pregnancy. For herd testing, at least 10 animals should be sampled and ideally should be resampled after intervention for any deficiencies. Criteria for the classification of trace mineral status are available. At most diagnostic laboratories, a toxicologist is able to provide reference ranges. Diagnosis and management of nutritional challenges in camelids have been reviewed.

Liver biopsies have been performed weekly under ultrasound guidance in llamas and alpacas without adverse effects9 and single blind samples may be performed safely. Risks associated with liver biopsy include hemorrhage, Clostridial hepatitis and peritonitis. Other problems include opening liver abscesses into the peritoneal cavity or missing focal lesions (granulomas, neoplasias, flukes). If these are suspected, fine needle aspiration under ultrasound guidance is preferred. This is performed with a 22ga, 6" needle, passed through an 18ga guide needle. Suction is placed on the needle with a syringe, the needle is redirection a few times and the suction released before withdrawing. These samples may be placed on a glass slide or submitted for culture.

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