Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

X. Exocrine Pancreatic Disease
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Spontaneous diabetes mellitus, as characterized by polyuria/polydipsia
(PU/PD), glucosuria, persistent hyperglycemia,
and loss of weight despite good appetite, has been
reported in a number of avian species, including budgerigars,
cockatiels, an Amazon parrot, an African grey parrot,
toco toucans, a red-tailed hawk, and the pigeon ( Altman
and Kirmayer 1976 ; Candeletta et al ., 1993 ; Lothrop et al .,
1986 ; Lumeij 1994c ; Murphey, 1992b ; Schlumberger 1956 ;
Spira, 1981 ; Wallner-Pendleton et al ., 1993 ; Wiesner, 1971 ;
Woerpel et al ., 1987 ).
The species that will be most commonly encountered
in clinical avian practice are budgerigars, cockatiels, and
toco toucans. A tentative diagnosis can be made by finding
glucose in the urine using a test strip (Testape, Eli-Lilly
Benelux NV, Amsterdam), whereas a definitive diagnosis
can be made by finding an elevated plasma glucose concentration.
PU/PD accompanied by glucosuria does not
always indicate diabetes mellitus. Diabetes mellitus can
only be diagnosed if elevated plasma glucose concentrations
have been demonstrated.
In mammals, Fanconi’s syndrome is known, characterized
by renal glucosuria, hyperaminoaciduria, and
hyperphosphaturia, as well as renal loss of potassium,
bicarbonate and water, and other substances conserved by
the proximal tubule. Fanconi’s syndrome should be considered
as the final result of any one of many possible primary
insults to proximal tubular function. The patient’s symptoms
reflect the disturbance of tubular function, in addition
to the primary cause of the syndrome. The syndrome may
be inherited or acquired.
There are some striking differences between birds and
mammals with regard to pancreatic control of carbohydrate
metabolism. In mammals, pancreatectomy results in diabetes
mellitus. Reported effects of pancreatectomy in birds
are controversial. However, the more recent experiments
performed on granivorous birds indicate that surgical extirpation
or destruction of the pancreas with cytotoxic agents
leads to hypoglycemic crisis and death. The few reported
pancreatectomies performed on carnivorous birds have
always led to diabetes mellitus. It is generally accepted
that glucagon is more effective in granivorous birds, which
exhibit a marked insulin insensitivity. The limited data
available on spontaneous diabetes mellitus in granivorous
birds suggest that in these species diabetes mellitus is not
caused by an insulin deficiency. Birds of prey may be
much more insulin dependent.
Spontaneous diabetes mellitus in birds has been
reported to be successfully treated with daily injections of
insulin in dosages comparable to doses used in dogs. These
successful treatments of diabetic birds (disappearance of
clinical signs) are surprising, considering the relative insulin
insensitivity that has been reported to occur in a variety
of avian species.
Plasma insulin and glucagon concentrations have been
established in three birds with hyperglycemia ( Lothrop
et al ., 1986 ). In all cases, insulin concentrations were similar
to those of controls, whereas glucagon concentrations, on
the other hand, were extremely high or extremely low. In
another case of diabetes mellitus (DM) in an African grey
parrot, Candeletta et al. (1993) reported extremely low
insulin concentrations. It is not clear whether these determinations
were accurate. The findings, however, suggest
that different etiologies were likely to be involved.
Speculations on possible etiologies of diabetes mellitus
in birds have been discussed ( Lumeij, 1994c ).
X . EXOCRINE PANCREATIC DISEASE
Exocrine pancreatic hormones that are present in the duodenum
of birds include amylase, lipase, trypsin, and chymotrypsin.
They facilitate degradation of carbohydrates,
fats, and proteins, respectively. The inactive precursors of
trypsin and chymotrypsin, trypsinogen, and chymotrypsinogen
enter the duodenum, where they are activated by
intestinal enterokinase. This mechanism prevents autodigestion
of pancreatic tissue ( Duke, 1986 ).
There are two basic manifestations of exocrine pancreatic
hormone disorders: (1) acute pancreatitis or acute pancreatic
necrosis, and (2) chronic pancreatitis resulting in
pancreatic fibrosis and pancreatic exocrine insufficiency.
The pathogenesis of acute pancreatitis involves the activation
of pancreatic enzymes in and around the pancreas
and bloodstream, resulting in coagulation necrosis of the
pancreas and necrosis and hemorrhage of peripancreatic
and peritoneal adipose tissue. Increased amylase and lipase
activities in plasma have been reported from birds with
active pancreatitis.
Reference values for plasma lipase and amylase have
been established in a population of 87 African grey parrots
(Van der Horst and Lumeij, unpublished observations).
α -Amylase activity in plasma was determined with a kinetic
p -nitrophenylmaltoheptaoside method (Sopachem α-Amylase
kit # 003-0311-00 Sopar-biochem, 1080 Brussels) at 30°C.
Values ranged from 571 to 1987 U/L (inner limits of P 2.5 to
P 97.5 with a probability of 90%).
Lipase activity was measured at 30° C using a test based
on the conversion of triolein by lipase to monoglyceride
and oleic acid. The associated decreased turbidity was
measured in the UV range (Boehringer Mannheim kit #
MPR 3-1442651). Reference values ranged from 268 to
1161 U/L.
Hochleithner (1989b) reported reference values for
plasma amylase in four different psittacine species using
a dry chemistry system (Kodak Ektachem, Amylopectin,
25°C; Kodak Company, 1986 ). The values were considerably
lower as compared to the ones just discussed: budgerigar
( n 50) 187 to 585 U/L, African grey parrot ( n 68 )
211 to 519 U/L, Amazon parrot ( n 30) 106 to 524 U/L,
and macaw 276 to 594 U/L.