Pancreas

Type I diabetes mellitus

insulin dependent, decreased insulin secretion, dogs > cats

beta cell atrophy, causes - chronic pancreatitis, immune-mediated, idiopathic, vacuolar, genetic

Type II diabetes mellitus

insulin independent, insulin resistance ± decreased insulin secretion, cats > dogs

multifactorial causes

Diabetes mellitus clinical signs

caused by hyperglycemia

hepatic lipidosis, diabetic neuropathy, PU/PD

Insulinoma

beta cell tumor

ferrets common benign, dogs and cats less common malignant

hypoglycemia, weakness, seizures, collapse

Glucagonoma

alpha cell tumor

rare in all species

hyperglycemia, hepatomegaly, superficial necrolytic dermatitis in dogs

Hypothyroidism

decreased thyroid hormone production → hair follicle cycle slows → predominance of telogen phase → friction alopecia

dogs > cats

dogs - lymphocytic thyroiditis or idiopathic atrophy

cats - iatrogenic

Goiter

thyroid hyperplasia

Causes - ingestion of goitrogenic compounds, deficient dietary iodine, excess dietary iodine, congenital

large animals, fish > others

neonates - dystocia, prolonged gestation, weakness, high mortality rate

Cat hyperthyroidism

adenomatous hyperplasia, adenomas > carcinomas

unilateral or bilateral, functional

hyperthyroid associated cardiomyopathy

Dog hyperthyroidism

carcinomas > adenomas

unilateral or bilateral, nonfunctional, expansile and invasive

early metastasis to lungs

Heart based tumors in dogs

thyroid carcinoma, hemangiosarcoma

chemodectoma - brachycephalics, benign, incidental, expansile

C-cell hyerplasia/neoplasia

high Ca → hypercalcemia → C-cell hyperplasia → neoplasia

dairy bulls, horses > dogs

often incidental

Hypoparathyroidism

Decreased PTH

Idiopathic parathyroiditis, surgery, secondary destruction - decreased Ca

Vitamin D toxicosis - increased Ca → metastatic mineralization

Hyperparathyroidism

Increased PTH, Ca and P variable

Clinical signs - vomiting/anorexia, PU/PD, generalized muscle weakness/lethargy, fibrous osteodystrophy

Primary - dogs > cats, horses, Increased serum PTH and Ca, Decreased P

Secondary nutritional hyperparathyroidism

low Ca diet, high P diet, vitamin D deficiency

Chief cell hyperplasia - increased PTH, variable P and Ca

Secondary renal hyperparathyroidism

Decreased GFR → increased P → increased PTH → chief cell hyperplasia

Decreased calcitriol → decreased calcium → increased PTH → chief cell hyperplasia

Metastatic mineralization

Pseudohyperparathyroidism

Humoral hypercalcemia of malignancy

Normal PTH, increased PTHrp → increased Ca and decreased P

Common in lymphoma, AGASACA, SCC

Juvenile panhypopituitarism

pituitary dwarfism

dogs >> others, german shepherds - genetic component, signs around 2mo

Cyst, usually in pars distalis → compression → atrophy

Stunted growth, abnormal dentition, open epiphyseal lines, puppy coat → alopecia

Decreased TSH/ACTH → death

Diabetes insipidus

Central - pituitary dependent - damage to pars nervosa, Decreased ADH → PU/PD, Dogs >> others

Nephrogenic - kidneys can’t respond to ADH

Pars distalis hyperplasia

Dog, rats > others, adenomas most common

Dogs - increased ACTH → adrenocortical hyperplasia bilateral → increased cortisol

Rats - increased prolactin → mammary gland hyperplasia/neoplasia

Pars intermedia hyperplasia

Horses - pituitary pars intermedia dysfunction → not equine Cushing’s

Increased beta-endorphins → docile, unresponsive to pain

Compression of hypothalamus → Hirsutism, hyperpyrexia, polyphagia

Compression of pars nervosa → PU/PD

Idiopathic adrenocortical atrophy (Addison’s)

Dogs, middle-aged females >> others

All 3 layers affected, bilateral

Addisonian crisis - decreased mineralocorticoids → increased K and decreased Na → PU/PD → hypovolemia, bradycardia → shock

Hypercortisolism (Cushing’s )

Pituitary dependent - functional pituitary tumor, Most cases, Increased ACTH → increased cortisol

Adrenal dependent - functional adrenal tumor, Dogs > cows, hamsters > others, Middle-aged, geriatric, Adenomas > others, Contralateral atrophy

Iatrogenic - steroid administration

Clinical signs - follicular inactivity leading to alopecia, catabolic effects leading to thin skin and muscle atrophy, hepatomegaly, panting, PU/PD

Medulla pheochromocytoma

Dogs, ferrets > horses, cows, clouded leopards, Catecholamines

Weakness, tachypnea/tachycardia, arrhythmias, hypertension

Exocrine pancreatic insufficiency (EPI)

Pancreas doesn’t make enough digestive enzymes → maldigestion and malnutrition

Clinical signs at >90% damage

Polyphagia, weight loss with muscle wasting, increased fecal volume, frequent defecation

diagnosis - decreased TLI

causes - pancreatic acinar atrophy, chronic pancreatitis, obstruction of pancreatic duct by space-occupying mass

Pancreatic acinar atrophy

most common cause of EPI in dogs, clinical signs 6-36 mo

breeds - German shepherd, rough-coated collies, eurasians

may be autoimmune-mediated disease targeting acinar cells

Pancreatic exocrine nodular hyperplasia

Dogs, cats, cattle, Incidental finding

Cause - age-related, regenerative response to injury

Grossly - multifocal raised, small, pale tan, well-circumscribed hyperplastic nodules

Exocrine pancreatic adenoma

Rare, often clinically silent

Local compression may result in atrophy or pancreatitis

Usually single/solitary, multiple with nodular hyperplasia, well-demarcated and encapsulated

Exocrine pancreatic adenocarcinoma

Most exocrine pancreatic tumors malignant, aggressive, Older dogs and cats

Clinical signs - abdominal pain, vomiting, weight loss, abdominal mass, +/- jaundice, +/- ascites

Often advanced by time of diagnosis - Marked local tissue invasion, Transcoelomic (intraperitoneal) metastasis, Metastasis to lung, liver, spleen, kidney

Acute necrotizing pancreatitis

Dogs, cats, horses, pigs - mainly dogs

Dogs - lethargy, anorexia, vomiting, diarrhea, fever and signs of abdominal pain

Severe cases - shock, DIC, sudden death

Risk factors - middle to older age, obese, female, small breed, high-fat diet, dietary indiscretion, underlying endocrinopathy, trauma, drugs, toxins, infectious disease

Diagnosis - leukocytosis, PLI, TLI, lipase, amylase

Pathogenesis - autodigestion of the pancreas from premature activation of pancreatic enzymes, self-destructive and self-perpetuating

Grossly - hyperemia, hemorrhage and necrosis, fibrinosuppurative exudation, peripancreatic fat necrosis, fibrinous adhesions to adjacent structures and omentum

Outcomes of acute necrotizing pancreatitis

Trypsin inhibitors inactivate trypsin → mild, self-limiting disease

Trypsin activates additional proenzymes → autodigestion cascade and acute clinical pancreatitis → severe disease or recurring bouts of pancreatitis

Severe disease - inflammatory mediators and activated digestive enzymes → shock, respiratory distress, DIC, death

Repeated bouts of pancreatitis → fibrosis and atrophy → EPI and diabetes mellitus

Chronic pancreatitis

Recurrent, intermittent attacks → morphologic and functional destruction of the gland

necrotic/inflamed foci → liquefied, sequestered or replaced by fibrous connective tissue → loss of pancreatic parenchyma + fibrosis → reduces functional pancreatic mass → EPI or diabetes mellitus

Gross lesions - small, shrunken, firm and nodular pancreas due to fibrosis

Microscopic - loss of pancreatic acini with replacement by fibrous connective tissue

Equine pancreatitis

Clinical signs - colic +/- shock

Pathogenesis - severe strongyle infestation → migration of larvae through pancreas → eosinophilic granulomas and/of fibrosis → pancreatitis

Sequelae to pancreatitis

Bile duct obstruction → post-hepatic jaundice

Anorexia and vomiting → hepatic lipidosis in cats

Hepatic necrosis → activated enzymes → autodigestion of adjacent liver → elevated liver enzymes

Peripancreatic fat necrosis - saponification

Severe acute pancreatitis → +/- temporary diabetes mellitus

Chronic pancreatitis → +/- permanent diabetes mellitus

Liquefactive necrosis of pancreas → pseudocyst formation, ascending bacterial infection leading to abscess

Peripancreatic inflammation (peritonitis) → peripancreatic fibrous adhesions