Maldigestion syndrome or disorder is also known as pancreatic insufficiency and EPI --Exocrine Pancreatic Insufficiency or Chronic Pancreatic Insufficiency. Unless the pancreas produces certain enzymes, digestion and proper absorption of food is not possible.
This condition is not exclusive to animals--humans can also suffer from it. It is also not exclusive to diabetics, as there are other non-diabetic disorders which can affect the pancreas.
Many pets and people suffer from this condition without having any type of diabetes. German Shepherds and rough-coated Collies are genetically predisposed to a condition called Pancreatic Acinar Atrophy, which would be a wasting or destruction of the digestive enzyme producing cells. 
Diabetes need not be a factor for this disease to occur, however, cats  with pancreatic insufficiency generally also have diabetes, due to damage of the endocrine pancreas as well as the exocrine area. It's suspected that chronic pancreatitis may be a more common cause of Exocrine Pancreatic Insufficiency in dogs than was previously thought. 
The pancreas has 2 regions--exocrine, which is responsible for production of digestive enzymes and endocrine--the area producing and excreting insulin.  Pancreatic insufficiency affects the exocrine, or non-insulin secreting sector of the organ, but when the condition is concurrent with diabetes, it increases the risk of hypoglycemia. 
The exocrine pancreas, which controls digestion.
The pancreas is primarily comprised of (approximately 82%) acinar cells,  which produce digestive enzymes needed to break food down into smaller molecules for absorption. Eating stimulates release of the body's digestive enzymes, in preparation for the later digestion/absorption process.
Exocrine pancreatic insufficiency
Without enough digestive enzymes to break down the food, nutrients cannot be absorbed properly by the cells lining the intestine. These are the cells that normally pass the nutrients into the bloodstream, where they go on to nourish bodily tissues.
If the food is not broken down enough for this process to occur, the nutritional value of the eaten food is not passed along to the rest of the body by these intestinal cells. When there are not enough pancreatic digestive enzymes, the nutrients remain in the intestine and leave the body in fecal matter, leaving body tissues undernourished.
One can be eating regularly and well, but the body is starving, due to the lack of the necessary enzymes to pass nutrients on to it. It's much like a poor diet and non-regular meals in the effect it has on the body; with either, the body fails to get the necessary nutrients to function normally.
An estimated 90% of the pancreas must be destroyed, therefore incapable of producing enough digestive enzymes, before there are symptoms pancreatic insufficiency. Note though that maldigestion need not be a pancreatic problem -- it can occur due to inflammation or lesions in the small intestine as well.
The signs are:
- rapid weight loss (caused by loss of body fat and atrophy of the muscles).
- Poor quality hair/fur coat in animals.
- Usually diarrhea with stools light-yellow or a whitish/grayish clay color, mostly loose or watery . If the diet contains a lot of fats, undigested fat may be visibly seen in the stool.
- Constant hunger, as seen in polyphagia,  to the point where non-food items like dirt, are eaten.
The animal acts and looks like it's starving --and it literally is because of its inability to properly use the food it eats. Sound nutrition and regular meals don't help in this case because the lacking enzymes are are the key to processing any food.
With diabetes, it's possible for a dog to have EPI issues but not show signs of fat in the stool (steatorrhea). 
Testing for the condition can involve blood tests to determine the amount of certain digestive enzymes in the blood and stool tests to determine the amount of digestive enzymes in it.
Treatment is by replacing the pancreatic enzymes.  with enzymes obtained from animal pancreases and given orally  Adding vitamins such as A, D, E, K and B12  may also be helpful, along with changing the diet to easily digested foods, which would mean they can be broken down and absorbed easier.
Normally, this treatment is for the lifetime of the person or pet; there have been cases in dogs where the pancreatic insufficiency has been temporary. Unfortunately, such cases are rare and most diagnosed with pancreatic insufficiency will remain on enzyme replacement therapy for life.
Here's help-message boards and e-mail lists
- EPI 4 Dogs Forums
- Canine EPI Mail List
- NOTE--Prior to joining the list, you must have a dog that has already been diagnosed with exocrine pancreatic insufficiency.
- EPI/Chronic Pancreatic Insufficiency. PetsHealth.
- Exocrine Pancreatic Insuffuciency. Pet Education.
- Wiberg, Maria (2003). Pancreatic Acinar Atrophy in German Shepherds & Rough-Coated Collies. University of Helsinki-Department of Clinical Veterinary Sciences.
- Pancreatitis. PetsHealth.
- Watson, PJ. (July 2003). Exocrine pancreatic insufficiency as an end stage of pancreatitis in four dogs. Journal of Small Animal Practice.
- Acinar Cell. Auckland Bioengineering Institute-University of Auckland. Cite error: Invalid
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- Caninsulin-Page 15. Intervet.
- Human Pancreatic Acinar Cell Carcinoma Case. Harvard University.
- Photo of Stool Before EPI Treatment. EPI4Dogs.
- Polyphagia. Petplace.com.
- Dog Weight Comparison Chart. Purina.
- Photos of Dog With EPI--Before and After Starting Treatment. EPI4Dogs.
- Greco, Deborah (2009). Dietary Treatment of Diabetes Mellitus in Dogs and Cats-Pancreatic disease. DVM 360.
- Fats: Nutritional Requirements & Obesity in Dogs. Pet Education.com.
- Drugs Affecting Digestive Functions-Pancrealipase. Merck Veterinary Manual.
- Enzyme Treatment. EPI4Dogs.
- PancreVed. 1-800 PetMeds.
- Pancrezyme. 1-800 PetMeds.
- Exocrine Pancreatic Insufficiency. Marvista Vet.
- Exocrine Pancreatic Insufficiency in Dogs EPI4Dogs-Very Helpful Website
- EPI In Dogs GlobalSpan
- Pancreatic Insufficiency in Dogs Drs. Foster & Smith
- Exocrine Pancreatic Insufficiency in Dogs Petplace.com
- Malabsorption in Dogs PetPlace.com
- Enzyme formulations MarkBrudnak.com
- Exocrine Secretions of the Pancreas Colorado State University School of Veterinary Medicine
- Exocrine Pancreatic Insufficiency-Dogs & Cats-Update Timoleon S. Rallis, K. Adamama-Moraitou, 2004, WSAVA
- Exocrine Pancreatic Insufficiency Hall, Edward J., 2003, WSAVA
- Drugs Affecting Digestive Functions Merck Veterinary Manual
- Laboratory Evaluation of Exocrine Pancreatic FunctionSteiner, Jörg M., 2008, WSAVA
- Chronic Diarrhea Steiner, Jörg, 2001, WSAVA
- Nutritional Management of the Most Common Digestive Diseases in Dogs and Cats Aulus Cavalieri Carciofi, Márcio Antonio Brunetto, 2009, WSAVA
- A quick review of canine exocrine pancreatic insufficiency Morgan, Jessica A., Moore, Lisa E., September 2009, DVM 360
- Canine EPI: Concurrent and secondary diseases Morgan, Jessica A., Moore, Lisa E., September 2009, DVM 360
- Exocrine Pancreatic Insufficiency ProVet UK
- Bacterial Overgrowth-Exocrine Pancreatic Insufficiency ProVet UK
- Juvenile Diabetes Mellitus Accompanied by Exocrine Pancreatic Insufficiency in a Dog Ji-Houn KANG, et. al., 2008, Japan Veterinary Medical Society
- Vetsulin-Diabetes-Related Diseases Intervet
- Helpful Laboratory Tests in the Diagnosis of Gastrointestinal Disorders Steiner, Jörg M., 2010, WSAVA