Hemoperitoneum in Horses

Monica Aleman • Johanna L. Watson

Hemoperitoneum is accumulation of blood in the abdominal cavity and can be a life-threatening problem. In the horse, associated causes are trauma; postoperative abdominal hemor­rhage; neoplasia; complications from pregnancy and foaling (utero-ovarian, middle uterine, and external iliac artery rupture); organ rupture; mesenteric injury; coagulopathies; ovarian hema­toma; systemic amyloidosis; and idiopathic hemoperitoneum.^7-13 The underlying cause is identified in the majority of cases (78%).¹³ Trauma (spleen and in mares, reproductive tract with associated vessels) and neoplasia are the most common causes of hemoperitoneum.^9,13

A recent retrospective study of 67 horses with hemoperi­toneum revealed that Thoroughbreds and Arabians were overrepresented breeds.¹³ Middle-aged and older horses (>13 years of age) and females may be overrepresented.^12,13 The most common clinical signs include abdominal discomfort, lethargy, hypovolemic shock, pale mucous membranes, pro­longed capillary refill time, tachycardia, and tachypnea.^12,13 Other clinical signs are anorexia, reluctance to move, weakness, trembling, cool extremities, and abdominal distention.¹²

Clinicopathologic abnormalities include anemia, neutrophilia, lymphopenia, thrombocytopenia, hypoproteinemia, hypocal­cemia, and azotemia.¹² Abnormalities in clotting parameters may be observed, depending on the cause.

Primary goals of therapy are treating hypovolemic shock, restoring perfusion and oxygen delivery to tissues, correcting fluid deficits, stopping further blood loss, and preventing complications. Blood transfusion should be considered if anemia becomes life threatening. The use of antifibrinolytic and procoagulant agents has been reported in the literature, but controlled studies on efficacy and safety in the horse with acute blood loss are lacking. Physical activity must be restricted in affected patients.

The short-term outcome is strongly associated with the underlying cause.¹³ Horses with neoplasia, uterine artery rupture, mesenteric injury, or disseminated intravascular coagulation (DIC) have a greater risk of not surviving. The survival rate has been reported to range from 51% to 74%.^12,13 Poor short-term outcome was significantly associated with high respiratory rate in one study.¹³ Prepartum hemorrhage appears to be associated with a poorer prognosis than postpartum hemorrhage (100% vs. 20% mortality, respectively).¹³

Hemothorax

Hemothorax may occur secondary to trauma (including lung biopsy), neoplasia, and strenuous exercise (see Chapter 31).¹⁵ Hemothorax in neonatal foals may be the result of lacerated lungs and vessels from fractured ribs (see Chapter 20).¹⁶

Exercise-Induced Pulmonary Hemorrhage

Exercise-induced pulmonary hemorrhage (EIPH) has not been identified as a major cause of blood loss. EIPH is associated with high-intensity exercise in horses. An estimated 14% to 75% of racehorses examined by endoscopy have EIPH.¹⁷ On the basis of a bronchoalveolar lavage analysis, a study suggested that 100% of horses performing strenuous exercise have EIPH.¹⁸ EIPH has been reported in various breeds. A recent study reported that the frequency of EIPH is associated with race type, distance, gender, and age. In one study, epistaxis was more common in females, older horses (vs. COX-1 than inducible COX-2 expression during states of inflammation), which will cause inhibition of prostaglandin E production, resulting in hypoxic or ischemic GI mucosal damage and delayed mucosal healing.²⁷

Ponies and young performance horses appear to be predis­posed. Clinical signs include inappetence, lethargy, intermittent or episodic colic, diarrhea, and weight loss. Clinicopathologic abnormalities may include mild anemia, moderate to severe hypoproteinemia with hypoalbuminemia, hypocalcemia, and in some cases azotemia. Although mild anemia is seen in most cases, horses occasionally present with severe anemia and hematochezia. RDC often develops over a period of days or a few weeks. The complete discussion of diagnosis and treatment is included in Chapter 32.