Cause of death determined for "Hank the Chimp" - | Chattanooga News, Weather & Sports

Cause of death determined for "Hank the Chimp"

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CHATTANOOGA (WRCB)—The necropsy report for Hank, a longtime resident of the Chattanooga Zoo, has been released.

Hank, who died in January, had fluid around his heart according to the University of Tennessee College of Veterinary Medicine's Department of Pathobiology.

The report noted, ""It appears based on the gross findings that this animal died due to heart disease with cardiac tamponade."

Dr. Danielle Reel released the final report.

According to Dr. Reel, the condition is, "a relatively common lesion in Chimpanzees.  This may prevent the ventricles and atria from filling properly and result in low stroke volume with subsequent systemic hypotension, shock and sudden death, which is the only clinical sign."

Zoo Director Darde Longs says the zoo's staff misses Hank every day and his death was due to aging.

"We know he had a great life here at the Zoo and the report points to the fact that Hank was simply facing challenges of aging.  We appreciate the time the University of Tennessee took in looking at everything possible in determining the cause of death of our beloved friend," says Long.

The full necropsy report follows.  The Chattanooga Zoo expects to receive a faxed version of the report later Monday.

Full Report


A 41 year old male neutered Chimpanzee weighing 55 kg is submitted for necropsy with a body condition score of 3 out of 5.  Postmortem decomposition is minimal.  The abdomen is distended.  The laryngeal air sacs are moderately distended with palpation.   There are three hard, silver- metallic, spherical, 0.3 cm in diameter foreign bodies distributed randomly throughout the subcutaneous tissues and underlying musculature.  The distribution is as follows:  embedded in the pectoral muscle 2 cm to the left of midline and 5 cm cranial to the xiphoid, embedded in the subcutaneous tissue at the level of the thoracic inlet to the left of midline, and embedded in the sartorius muscle at the level of the pubis to the left of midline.  Bilaterally, coxofemoral joints are circumferentially rimmed by multifocal to coalescing nodular, white, irregular bony

growths (osteophytes); proliferations are along the margin of the acetabulum and femoral head with extension onto the femoral neck.  Bilateral irregular cartilage erosions are located along the proximal aspects of the trochlear grooves of the femurs.  On the margin of both patellas, there are minimal, regionally extensive, irregular, rough bony growths (osteophytes).  Right femoral bone marrow is diffusely dark red and floats in formalin.  Pericardial effusion is golden and measures 650mL.  The heart weighs 460 g (0.84% of total body weight).  There are multifocal to coalescing irregularly round, white, firm depressions in the epicardial surface of the right ventricular myocardium with extension towards the apex. These areas of pallor extend into the myocardium on cut section. The depressions range in size from less than 1 mm to 0.3 x 0.3 cm.  On the intimal surface of the aortic outflow tract there is a slightly raised, focally extensive, linear, white, firm, rough lesion measuring 2 x 0.5 cm.  There is a focal, irregular, minimally raised, red, soft plaque measuring 0.7 x 0.6 cm on the endocardial surface of the left atrium dorsal to the left atrioventricular valve.  The left middle lung lobe is dark pink and collapsed (suspect atelectasis).  Cranial, middle, and caudal right lung lobes are pale pink and spongy; all sections float in formalin.  Throughout the abdominal cavity, there are multifocal to coalescing thin bands of firm, white (fibrous) adhesions between the omentum and the viscera.  The gallbladder wall measures 0.2-0.3 cm in thickness and the bile duct is patent.  The liver weighs 1.74 kg (3.2% of body weight). A widespread reticular pattern is seen over the capsular surface of the liver.  Liver lobe edges are diffusely rounded.  On cut section the liver is mottled tan and dark red. The liver is mildly friable and does not float in formalin.  The stomach and intestines are moderately to markedly distended with gas (postmortem).  Scattered dark red to purple petechiae and mucosal vessels are diffusely congested on the mucosal surface.  Multifocally adhering intestinal loops are multifocal, thin, white, firm (fibrous) bands.  On the ventral aspect of the brainstem, at the level of the Pons, the basilar artery is multifocally thickened firm and white; lesions range in size from 0.3 x 0.1 x 0.1 cm to 1 x 0.2 x 0.1 cm and appear to fill the vessel lumen on cut section.



Marked hydropericardium

Multifocal to coalescing chronic myocardial and epicardial fibrosis

Mild chronic focal endocardial erosion (jet lesion, left atrium)

Moderate chronic multifocal atherosclerosis (aortic outflow tract, basilar artery at Pons)

Hepatic congestion

Multifocal chronic fibrous omental and visceral adhesions

Multifocal subcutaneous and muscular metallic foreign bodies (chronic gunshot wound) (pectoral muscle, sartorius muscle, and the level of the thoracic inlet)

Marked chronic bilateral osteoarthritis with marked osteophyte formation (coxofemoral joints)

Moderate chronic multifocal to coalescing bilateral osteoarthritis with minimal osteophyte formation (stifle joints)

Reactive bone marrow


Slide 1:  Brain (corona radiata):  There is minimal congestion of meningeal vessels with rare perivascular meningeal hemorrhage.  Multifocal neurons are surrounded by up to 5 glial cells (satellitosis). Rare neurons contain intracytoplasmic golden pigment (lipofuscin).  Rare, random neurons are shrunken, hypereosinophilic and angular. 

Slide 2:  Brain (hypothalamus):  Neurons multifocally contain variable amounts of golden brown pigment. There are frequent lightly basophilic, variably sized, spherical concretions throughout the neuropil, but primarily within the white matter (brain sand). 

Slide 3: Brain (internal capsule):  Neurons multifocally contain variable amounts of golden brown pigment.

Slide 4: Brain (hippocampus): Neurons multifocally contain variable amounts of golden brown pigment.

Slide 5:  Basal artery plaque:  The plaque is not represented in section. Neurons multifocally contain golden granular pigment.  

Slide 6:  Cerebellum:  Neurons multifocally contain variable amounts of golden brown pigment.

Slide 7:  Brain stem (pons):  There are multifocal areas of minimal perivascular hemorrhage.  Multifocal neurons contain intracytoplasmic golden and brown granular pigment (lipofuscin).  Near the choroid plexus, there are multifocal lightly basophilic spherical concretions (brain sand).

Slide 8:  Pituitary gland: Throughout the parenchyma there are irregular, unencapsulated proliferative nodules in the pars intermedia; these lesions are minimally compressive and cells are piled up and larger with increased cytoplasm.

Slide 9:  Bone marrow:  There is 50% cellularity with an M:E ratio of 2:1.  All cell lines are represented and iron stores are adequate.

Slide 10:  Heart (left ventricle):  Approximately 30% of the left ventricular free wall has been replaced by dissecting bands of fibrous connective tissue.  Cardiac myocytes trapped within fibrosis are atrophied and angular and frequently have karyomegalic nuclei.  Cardiac myocytes surrounding areas of fibrosis are haphazardly arranged with karyomegalic nuclei (hypertrophy). 

Heart (right ventricle):  The findings are similar to those described in the left ventricle and fibrosis replaces approximately 10% of the wall.

Slide 11:  Left atrium (jet lesion):  Lining the endocardial surface is a raised, variably thickened irregular plaque extending from the surface.  This raised plaque is composed of irregular bundles of fibrous connective tissue mixed with basophilic myxomatous material and small to moderate numbers of foamy macrophages. The findings in the adjacent atrial myocardium are similar to those described previously.

Heart (interventricular septum): The findings are similar to those described previously.

Slide 12:  Aorta: Diffusely elevating the tunica intima are multifocal to coalescing areas of basophilic myxomatous stroma mixed with mineral and moderate numbers of foamy macrophages. 

Slide 13:  Epicardial fibrosis:  The findings are similar to those described previously; fibrosis replaces approximately 30% of the cardiac myocytes. 

Slide 14:  Epicardial fibrosis:  The same findings as seen in slide 10 with fibrosis replacing 20% of the myocardiocytes.  Rare aggregates of brown granular pigment are seen adjacent to vessels (hemosiderin) and within macrophages.

Slide 15: Axillary lymph node (right):  Diffusely medullary sinuses are ectatic and contain eosinophilic homogeneous material mixed with minimal blood.

Adrenal (left):  Many adrenocortical cells have karyomegalic nuclei.  There is a focally extensive area with loss of nuclei in the cortex; this area is replaced by eosinophilic fibrillar to smudgy material.  A Masson's trichrome stain highlights this eosinophilic material light blue (fibrosis).

Liver:  Multifocally centrilobular sinuses are moderately ectatic with compression and thinning of adjacent hepatic cords. Aggregates and hemosiderin and siderophages are within the congested areas. Random, individual hepatocytes have cleared nuclei with variably marginated chromatin (glycogen).  Multifocal hepatocytes are binucleated and minimally swollen. There are multifocal portal and random rare aggregates of lymphocytes. 

Slide 16:  Adrenal (right):  There are multifocal variably sized irregular to distinct nodules composed of cortical cells. The inner cortical region contains golden pigment-laden cortical cells.  Medullary sinuses are multifocally congested and multifocally moderately ectatic. 

Liver:  The same changes as seen above with diffuse subcapsular congestion.  There is a mild increase in the number of bile ductule profiles.

Spleen:  Central regions of lymphoid follicles contain small amounts of eosinophilic, irregular smudgy material (amyloid, Congo red stain).

Slide 17:  Gall bladder:  There is diffuse autolysis. 

Colon:  There is diffuse moderate autolysis. 

Slide 18:  Jejunum: There is diffuse moderate autolysis of the mucosal surface.  Rare crypts are absent. 

Pancreas:  There is multifocal autolysis. There is minimal multifocal to coalescing interstitial fibrosis.

Slide 19: Stomach (fundus): There is diffuse minimal to moderate autolysis of the mucosal surface.  Moderate aggregates of rod bacteria are on the mucosal surface.

Liver:  The changes are similar to those seen above, in slide 15.

Slide 20: Stomach:  No significant lesions.

Urinary bladder: Submucosal vessels are diffusely congested. 

Slide 21:  Large intestine:  The mucosal surface is diffusely autolyzed. 

Slide 22:  Skeletal muscle:  Rare myocytes are vacuolated, swollen (degeneration).

Slide 23:  Lung:  Alveolar spaces multifocally contain scant amounts of eosinophilic fibrillar and homogeneous material (fibrin & edema) mixed with hemorrhage, alveolar macrophages, hemosiderophages (heart failure cells) and rare multinucleated giant cells. Giant cells often contain hemosiderin pigment and phagocytosed refractile material. In one area, near the pleural surface, alveolar septa are moderately expanded by fibrosis and multifocally collapsed (atelectasis).  Vessels are multifocally surrounded by few lymphocytes, are diffusely moderately congested, and rarely have focal thickening of the tunica media.  Rare, irregular deeply amphophilic aggregates of material forming distinct layers are multifocally scattered throughout alveolar spaces (mineralization).  The pleural surface is minimally thickened.  Mesothelial cells are multifocally hypertrophied. 

Slide 24:  Lung:  The findings are similar to slide 23 with increased numbers of multinucleated giant cells phagocytizing debris and red blood cells (erythrophagocytosis). 

Slide 25:  Lung: The findings are similar to slide 23.  

Slide 26:  Kidney:  There is diffuse cortical and medullary interstitial congestion.  Focal segmental glomerular tufts are also diffusely congested.  Multifocal aggregates of few lymphocytes, plasma cells and fewer macrophages mixed with fibrosis are expanding the cortical interstitium.  In these areas of inflammation and fibrosis there is occasional tubule loss. Renal tubular epithelium multifocally contains intracytoplasmic brown pigment and tubular lumens contain golden brown homogeneous material.  Rare multifocal medullary tubules have been replaced with fibrous tissue.

Slide 27:  Kidney:  The findings are similar to those seen in slide 26. The section contains a focal ectatic medullary tubule lined by cuboidal epithelium.



Brain:  Neuronal cytoplasmic lipofuscinosis (aging change)

Pituitary gland: Multifocal nodular hyperplasia of the pars intermedia

Left atrium (jet lesion): Moderate chronic focally extensive intimal fibrosis

Aorta: Moderate chronic arteriosclerosis

Heart:  Moderate to marked chronic multifocal to coalescing myocardial fibrosis and rare arteriosclerosis

Liver:  Moderate chronic centrilobular sinusoidal congestion

Adrenal gland (left):  Mild chronic focal adrenocortical fibrosis

Adrenal gland (right):  Moderate chronic multifocal adrenocortical nodular hyperplasia

Spleen: Mild multifocal amyloidosis

Lung:  Moderate chronic multifocal alveolar histiocytosis with hemosiderophages (heart failure cells), atelectasis, pulmonary edema and fibrin



Kidney, Liver, Spleen, Skin, Fat, Lung, Stomach contents, Urine (temporarily retained frozen)



Idiopathic myocardial fibrosis and sudden cardiac death



Idiopathic interstitial myocardial fibrosis is a relatively common lesion in Chimpanzees. Males are more commonly affected than females. The cause of fibrosis has not been identified. Gross and histologic findings in this case are similar to previous reports of this entity; article references for this condition have been included below. The amount of pericardial effusion in this case likely resulted in cardiac tamponade.  Accumulation of fluid in the pericardial sac will result in increased pressure on the heart. This may prevent the ventricles and atria from filling properly and result in low stroke volume with subsequent systemic hypotension, shock and sudden death. The presence of fibrosis in the myocardial wall, could also have altered electrical conduction through the heart and resulted in a fatal arrhythmia. Sudden death can be the only clinical sign.  Additional evidence of congestive heart failure was seen histologically in the lungs and liver. 


Multifocal areas of arteriosclerosis and splenic amyloid deposition were identified and these are relatively common findings in nonhuman primates. In this case, they are considered to be incidental lesions. Few pieces of shot were found in the muscle and subcutaneous tissues; this finding represents a chronic healed lesion and played no role in the death of this animal.

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