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Anaphylaxis-related Hemoabdomen

Posted by Dr. Stephanie Lisciandro, DVM, DACVIM (SAIM) on Apr 4, 2019 3:16:30 PM


An 18 month old F/I Yorkshire Terrier presented to the emergency room for acute onset of vomiting. Once arriving at the ER, her signs progressed with marked weakness, tachycardia, hypothermia, and hypotension. An initial “FAST” exam did not show any free fluid in her abdomen. She was admitted for fluid therapy and supportive care.

Laboratory findings: HCT 63%, platelet count 120,000; BUN 33 mg/dl, ALT 622 U/L, GGT 45 U/L; baseline cortisol normal; SNAP cPL abnormal; the next morning, chemistry profile showed albumin 2.0 g/dl, globulin 2.0 g/dl, ALT out of range, GGT 27 U/L

The next morning an ultrasound was performed with the following findings: Gallbladder wall edema, moderate volume peritoneal effusion (abdominal fluid score 4/4) and diffuse gastric changes (suggestive of non-specific gastritis).

In addition to the gallbladder “halo sign” (discussed in the January 2019 blog), she had developed abdominal effusion.  Coagulation times were out of range.  It is important to recognize that dogs can develop anaphylaxis related hemoabdomen.  Recognition is vitally important because these are non-surgical cases and the hemoabdomen will resolve with successful treatment of anaphylaxis (AX). 

Dogs with anaphylaxis commonly develop abdominal effusion.  The effusion is often scored as an abdominal fluid score (AFS) of 1 or 2 using the AFAST-applied fluid scoring system, and are most commonly positive at the FAST DH view (which makes sense due to acute hepatic venous congestion and hepatic swelling). These low-scoring effusions (AFS 1 and 2) are often self-resolving, and the canine patient is non-coagulopathic (PT, aPTT < 25% over upper reference range).  In this case, the volume is generally too small for safely performing abdominocentesis. Serial AFAST with AFS (repeat AFAST 4- hours post-admission) is justified to detect worsening of effusion (increasing score [AFS]) or resolution (decreasing score [AFS]) or static (no change in score [AFS]). If the volume of the effusion is increasing, a repeat PCV/TS and coagulation profile is indicated.

Other cases of canine anaphylaxis have large volume effusions of AFS 3 and 4 which have the character of hemoabdomen.  It should be noted that patients with anaphylaxis related hemoabdomen have a normal or increased PCV in conjunction with the hemoabdomen. This should be a clue that anaphylaxis may be involved whereas, a bleeding patient with an AFS 3 to 4 will likely have anemia.  Even in patients with large volume effusions, the coagulation profile may be close to normal and stay close to normal (less than < 25% over upper reference range) on repeat PCV/TS and Coagulation Profile 4-hours post-admission. Others will have coagulation times that are out of range.  These large volume effusions will generally self-resolve within 24-hours if the patient responds favorably to initial resuscitation and therapy for AX including fluid resuscitation +/- epinephrine, histamine-1 receptor blocker (diphenhydramine), histamine-2 receptor blocker (famotidine), and glucocorticoids (dexamethasone sodium phosphate or prednisone). Abdominocentesis should be performed if the free fluid is safely accessible.

In our experience, these effusions are hemorrhagic with a comparative abdominal PCV of minimally ≥ 50% of the peripheral PCV. In canine AX cases with abnormal coagulation profiles (greater than > 25% over upper reference range), clotting factors should be replaced as soon as possible, e.g., fresh frozen plasma (FFP). As a crude guideline, 1 in 5-7 canine AX cases require FFP, and 1 in 20 canine AX cases require pRBCs. Some of the coagulopathic canines require repeated FFP over several days but more than 1 round of FFP is uncommon if antihistamines and glucocorticoids are used initially to block the second episode of anaphylaxis which leads to persistent continued coagulopathy (WOA Guidelines). The author treats all canine AX cases with diphenhydramine (H1 receptor blocker) once, famotidine (H2 receptor blocker, mitigates vascular permeability) for several days, and importantly a 5-7 day tapering regimen of anti-inflammatory dosing of prednisone to attenuate the second episode (wave) of AX-related inflammation that propagates and perpetuates coagulopathy. Glucocorticoids must be administered at the time of presentation (initially immediately after fluid resuscitation) and then continued in anti-inflammatory dosages over the next 5-7 days.

It is important to recognize the limitations and additional rule outs for the sonographic finding of a gallbladder "halo sign"; and that dogs have a unique anaphylaxis-related, heparin-induced, medically-treated hemoabdomen complication, and not over-react to stable patients with normal to relatively normal clotting times (less than < 25% over upper reference range) since many will self-resolve with standard AX therapy.  In other words, many dogs with mildly abnormal coagulation profiles will resolve without transfusion products. Equally important is to recognize the anaphylactic patient and not to take an AX-related coagulopathic canine hemoabdomen to surgery, which could be catastrophic for the dog, potentially resulting in death. Larger case studies and more sophisticated coagulation assessment are needed to fully understand this perplexing canine AX-related phenomenon. 

Please direct questions to slisciandro@oncurapartners.com

Click Here For Treatment Sheet For Canine Anaphylaxis

Some excerpts with permission from Gregory Lisciandro at FASTVet.com.

Topics: Veterinary Ultrasound, Animal Ultrasound, Oncura Partners