I am proud to be a veterinarian. Think of all the diagnostic and therapeutic advancements we have seen. These aren't esoteric. We all use them literally every day. How did we survive before advanced imaging, cage side testing like SNAP or endoscopy and organ function testing? Now, Houston pets have access to artificial joints and lithotripsy. Collapsing tracheas, urethral strictures and ureteral stones were once life ending.  We now place a stent and life goes on. What about those new diseases? Pet food now supplies enough taurine and potassium that feline DCM & hypokalemic myopathies have slipped nearly to extinction. Most of us remember before Ehrlichia hitched a ride from Viet Nam and introduced a myriad of disease syndromes. Remember when parvovirus affected only cats? Hepatic lipidosis and FIV did not even exist until after I moved to Houston!

Well we're witnessing the birth of another disease. In the last 6 months we've been presented with 3 cats that proved to have a disease none of us had previously seen. The name is Feline Gastrointestinal Eosinophilic Sclerosing Fibroplasia (FGESF). This is an inflammatory process found in the gastrointestinal tract of cats. Eosinophils are the primary and distinguishing cells seen, and there is a lot of fibrosis (so there is often a palpable mass present). Once again you are on the front lines as we try to document and understand this unique disease. Currently we don't know the incidence because we haven't been looking for it. When discovered, our 3 cases were so advanced, treatment options were limited and the prognosis was poor. But we can change that if we work together and learn to recognize the early clues there is nothing irreversible about this disease. We've got several questions to answer. I'd like to know incidence, when to be suspicious, best method to establish a diagnosis, treatment at various stages and prognosis at each stage with and without treatment.

Clinical Features

There were no distinguishing clinical features in 25 cases that were retrospectively studied and described (reference 1). The age range was 14 weeks to 16 years and both males and females were seen (though 72% were males). There were 14 DSH & 4 DLH and one each of various pure bred cats. This distribution fits Houston's cat population. The above mentioned fibrosis produces a hard abdominal mass. Indeed a palpable mass was identified in all 25 cats of the above cases (most were post mortem).

There is hope for earlier diagnosis because abdominal ultrasound discovered all 3 of our cases. Essentially this is an ulcerated intramural mass (figures 1&2) and is found most commonly at the pyloric sphincter or ileocolic junction (21/25). All 3 of our cases were at the pyloric sphincter. Mesenteric lymphadenopathy with similar inflammation and fibroplasia was present in 7/25 cats and all 3 of our cases. Clinical signs are as expected for an ulcer or obstructing abdominal mass or both. Hence vomiting and weight loss were present in 84% and 68% respectively. Disease duration was days to weeks. When the pyloric mass grew into the common bile duct, hyperbilirubinemia and icterus were present (3/25). The pancreas was infiltrated in one cat. A perforating ulcer quickly progressed to terminal peritonitis in one cat.

Laboratory Findings

Lab work should make you suspicious. Peripheral hypereosinophilia was present in 58% of the cats reflecting one of the distinguishing histological findings. It was present in all 3 of our cases. Eosinophilia in a sick, vomiting cat should immediately alert us to Addisons or an eosinophilic inflammatory disease. I would expect a variable inflammatory leukogram (infected ulcer). The biochemistry profile would reflect vomiting and dehydration and hence variable hypokalemia and hypernatremia. Dehydration could mask a variable hypoproteinemia and anemia. Hypovolemia should result in lactic acidosis. But if the mass causes an obstruction anterior to the pancreatic duct, the cat could lose acid in the vomit, but retain bicarbonate excreted from the pancreas. This would cause alkalosis and the proverbial paradoxical aciduria. (Due to low chloride the kidneys excrete H+ ions in exchange for Na+ to maintain electrical neutrality). Hyperbilirubinemia and elevated liver enzymes will occur if the mass obstructs or infiltrates the common bile duct. Once you correct dehydration a regenerative anemia with hypoproteinemia would reflect whole blood loss from the ulcer. Of course it's a cat and their wimpy marrow may present the usual nonregenerative anemia of chronic disease. Not to mention iron stores could be low if blood loss is chronic. Then we would expect a microcytic, hypochromic (small pale cells) nonregenerative anemia from iron deficiency.

In addition to eosinophils, histopathology reveals branching and anastomosing trabeculae of dense collagen. These cords of collagen are separated by a densely cellular population of large spindle-shaped cells. The trabecular collagen merges gradually into typical granulation tissue. All lesions contained variably dense infiltrates of eosinophils, and mast cells. There are fewer neutrophils, lymphocytes and plasma cells. The lesions started at the mucosa and extended a variable distance into the wall but did not extend beyond the serosa (except when extending to the bile duct, pancreas or lymph nodes). This limitation is helpful because you are going to think this is cancer at exploratory surgery and wonder if you should euthanize on the table. Cancers don't respect boundaries. This disease seems to. Lymph node histology was similar to the sclerosing lesions of the intestines or it was limited to an eosinophilic lymphadenitis.

Aspiration Cytology Reflects Histopathology

If you palpate one of these abdominal masses and aspirate it you should exercise caution with interpretation. We are all products of our past and I can already anticipate mistaken conclusions I'll conjure up. If I aspirate a collagen cord it will be nearly acellular and I'll conclude I am feeling an acellular foreign body. While surgery maybe the correct decision my prognosis could be misleading. If I hit the dense band of spindle cells, I will think there is a sarcoma (leiomyoma / sarcoma, fibrosarcoma etc). If I get the inflammatory reaction in some places, it will be eosinophils and in other areas mast cells or both. Either would make me suspicious for a mast cell tumor. If I aspirate the granulation tissue you'll see a mixture of inflammatory cells with epithelioid macrophages. Then FIP or deep fungi will come to mind. Be careful as one site may not represent the whole.

Bacteria were seen in 14 of the 25 cats (56%). These included gram negative rods, gram positive rods and gram positive cocci. E. coli and Clostridium were identified from the wall of the only case that was cultured. It is unproven whether bacteria are a primary or secondary event. Certainly ulceration exposes the bowel to luminal bacteria allowing invasion. Still, the referenced paper hypothesizes they are part of the pathogenesis. They surmise that the pyloric and ileocolic sites are prone to physical forces and that results in foreign-body penetration. Thus bacteria are implanted that then initiate the response. Given the areas involved I can see how hair etc. could penetrate into those sites implanting bacteria and fungi. They go on to suggest previous antibiotic usage or the exuberant inflammatory response may limit our ability to find bacteria with histopathology (+ in only 56%). The one case I saw with an endoscope we picked hair out of the ulcer. It was not sitting on the surface or in the ulcer like hair packed into a crater. It had to be pulled out in small pieces as if it was implanted. 

When to suspect FGESF

1-      I feel a firm abdominal mass especially upper right quadrant or at the cecum

2-      AUS finds an abdominal mass especially in the pyloric and ileocolic regions

3-      GI obstructions especially with a thickened area of bowel

4-      GI work up reveals an ulcer especially when distal to the stomach

5-      Unknown cause of chronic vomiting

6-      Unknown cause of chronic weight loss

7-      Unexplained eosinophilia especially with any suspicion of GI signs

While bacterial implantation is an attractive theory, antibiotics alone have not improved outcome. Only cats treated with corticosteroids had a significantly longer survival time than those receiving other treatments. That does not discount the infection hypothesis. Remember cats are prone to eosinophilic syndromes. The Eosinophilic granuloma complex is common in clinical practice. These include indolent ulcers, eosinophilic plagues, eosinophilic granulomas and less commonly a hypereosinophilic syndrome. Remember they are believed to be started by viruses, bacteria and fungi. Those that go on to develop the eosinophilic granuloma complex are thought to have an inherited eosinophil dysregulation. This leads to an inappropriate eosinophilic inflammatory response. Could FGESF have a similar pathogenesis?

Considering this is a new illness still being described it could easily be confused with other processes even between pathologists. While clinical and histologic features collectively provide differentiation in most cases, other cases may require histochemical and immunohistochemical stains for a definitive answer. I can remember a case years ago with an ileocolic mass and what I now know as typical histopathology. Back then the pathologist and I finally called it FIP because it had some pyogranulomatous features. But we both knew it didn't fit. We simply could not find anything else to call it. Please consider FGESF when histopath from any intestinal mass comes back with the following diagnosis:

1. Eosinophilic granulomatous disease
2. Feline intestinal Sclerosing mast cell tumor
3. Gastrointestinal Stromal Tumor
4. Fibrosarcoma

Lifesaving treatment is yet to be defined. Perhaps one treatment won't fit all. It may depend when it is discovered as to what is best for the patient. We don't have answers only questions at this time. Clearly we are seeing the birth of a previously unrecognized disease. We've seen 3 in less than 6 months because we now know it exists. How about you? Perhaps you've already seen one or more of these and like me, just didn't know what to call it or how to file away the information. Please call me when you see one of these cases. Together we can surely put together enough data to better understand this disease. As always your input is invaluable.

1 Craig LE, Hardam EE, Hertzke DM et al: Feline Gastrointestinal Eosinophilic Sclerosing Fibroplasia. Vet Pathol46:63-70, 2009