Ultrasonographic and clinicopathological features of pyloroduodenal adenomatous polyps in cats

Abstract

Objectives

The aim of the study was to report the ultrasonographic and clinicopathological findings in cats with confirmed pyloroduodenal adenomatous polyps.

Methods

Clinicopathological data, ultrasonographic and histopathological findings were collected retrospectively from medical records.

Results

Pyloroduodenal polyps appeared as small moderately echogenic and homogeneous nodules filling most of the proximal duodenal or pyloroduodenal lumen. The most common presenting signs in this study included acute vomiting and anorexia in 4/6 cats and lethargy in 3/6 cats. Two cats presented with severe anemia, suggestive of active bleeding. One cat presented with increased bilirubin without anemia, suggestive of impaired bile flow. Five cats survived surgical removal of the polyp and were free of clinical signs 817 days after the procedure.

Conclusions and relevance

Pyloroduodenal polyps have subtle ultrasonographic changes that can easily be mistaken for ingesta. They are characterized by a discrete small (up to 1.5 cm in diameter) homogeneous echogenic nodule filling the pyloroduodenal lumen. Pyloroduodenal polyps are benign lesions but can cause severe clinical signs including gastrointestinal bleeding or biliary obstruction. The prognosis is excellent with surgical removal.

Introduction

Polyps are morphologically defined as the abnormal growth of tissue originating from the mucosa. ¹ In most publications, the term polyp is used to define a benign lesion arising from an epithelium.^1–4 Adenomatous polyps are a subcategory of polyps composed of moderately atypical glandular epithelium surrounding the lamina propria. ³ An extensive report on adenomatous polyps of the duodenum in 18 cats is available. ⁴ The majority of cats in that study were castrated males, with an over-representation of Asian ancestry and a median age of 11.8 years. On histological examination, 10/18 cats had polyps originating from duodenal mucosa, six from pyloric mucosa, two from a mixture of pyloric and duodenal mucosa. ⁴ None of the cats had any signs of malignant transformation at the base of the polyps and none developed adenocarcinoma of the proximal duodenum and pylorus during the follow-up period ranging from 1 to 49 months. ⁴

Polyps can be asymptomatic except when they occlude the lumen of the gastrointestinal tract or when they become ulcerated.^1,2 Vomiting is the most common reported clinical sign, often accompanied by anorexia and lethargy.^1,3–5 Anemia, diarrhea and melena are not common but are reported when there is ulceration of the polyp or the surrounding tissues.^1,4 Significant laboratory abnormalities are not usually seen unless there are secondary alterations due to vomiting, intestinal obstruction, blood loss from ulceration or biliary obstruction.^1,4,5

To date, the ultrasonographic features of adenomatous duodenal polyps in cats have not been reported. While this disease can be asymptomatic, it can also lead to severe intestinal bleeding, gastrointestinal obstruction and possibly biliary flow compromise. Identifying and differentiating this benign lesion from other gastrointestinal lesions is important as it has been reported to carry a good prognosis and resolution of clinical signs with surgical resection. ⁴ Early identification and resection of this lesion can also prevent the progression and severity of clinical signs. The purpose of this study is to report the ultrasonographic, clinical and histological finding in cats with confirmed pyloroduodenal polyps.

Materials and methods

The medical records of six cats with histologically confirmed pyloroduodenal polyps were reviewed. Four cases were managed at the Cummings School of Veterinary Medicine at Tufts University from January 2001 to June 2014, and two cases were identified in the Montreal region – from the Centre Vétérinaire DMV and South Shore Veterinary Center, respectively. Criteria for inclusion were abdominal ultrasound examination and histological confirmation of a pyloroduodenal polyp by endoscopic or surgical biopsies. All procedures were performed in the hospital where the case was imaged (Cummings School of Veterinary Medicine at Tufts University, Centre Vétérinaire DMV and South Shore Veterinary Center, respectively).

A board-certified pathologist (SJ) reviewed the histology slides of the four cases managed at Tufts University and diagnosed the condition, using previously described criteria. ⁴ For the two additional cases, diagnosis was made based on the available pathology report from two board-certified pathologists. These reports were reviewed by the pathologist (SJ) to ensure consistency of the findings. Adenomatous polyps were identified as exophytic growths composed of tubules supported by a fibrovascular core resembling or extending from the lamina propria. Adenomatous polyps were differentiated from hyperplastic lesions by the presence of mild dysplasia, branching crypts, mitotic figures above the crypt base and/or some loss of basal nuclear polarity. Adenomatous polyps were differentiated from carcinomas by the lack of stromal invasion and presence of only mild dysplasia or cellular atypia.

Ultrasonographic still images and/or video clips were all reviewed by the same board-certified radiologist (DP). They were assessed for lesion location, shape, size, echogenicity, vascularity, wall thickness and layering appearance, gastric distension and size of regional lymph nodes. The echogenicity of the lesion was subjectively labeled moderately echogenic if similar in echogenicity compared with the adjacent normal submucosal layer, and classified as homogeneous/inhomogeneous if the degree of echogenicity was uniform/or not throughout the lesion. Color Doppler was performed in 2/6 cases and the images were reviewed. Gastric, pyloric or duodenal wall layering was considered normal, altered or lost.^6–8

Results

Six cats were included in the study. All cats had physical examination, blood cell count, chemistry profile, abdominal ultrasound and histopathological reports. Cats had a mean ± SD age of 9.6 ± 3.5 years. Mean ± SD weight was 6.7 ± 1.2 kg. Breeds included domestic shorthair (n = 3), domestic mediumhair (n = 1), domestic longhair (n = 1) and Ragdoll (n = 1). All cats were neutered (four castrated males and two spayed females).

The most common reasons for presentation included acute vomiting and anorexia in 4/6 of the cases and lethargy in 3/6 cases. Other clinical signs reported were diarrhea (2/6), hematemesis (1/6) and melena (2/6).

On presentation, mild-to-moderate dehydration was present in 4/6 cats. Abdominal palpation was normal in all cats. Severe anemia (hematocrit of 8% and 15%, respectively) was noted in two cats. The anemia was moderately regenerative (reticulocyte count of 106,000/µl and 108,000/µl, respectively) with normal mean corpuscular volume (51.6 fl, reference interval [RI] 41.0–58.0 fl; and 43.6 fl, RI 38.9–50.3 fl, respectively) and normal mean corpuscular hemoglobin (18.58 pg, RI 12.00–20.00 pg; and 14.3 pg, RI 12.9–17.0 pg, respectively). Both cases also had decreased total solids (4.4 g/dl, RI 5.7–8.9 g/dl; and 5 g/dl, RI 5.7–8.9 g/dl, respectively). Mild increased bilirubin (0.9 mg/dl [15 µmol/l], RI 0.0–0.4 mg/dl [0-6.8 µmol/l]) associated with severe increased feline pancreas-specific lipase (13.4 µg/l, RI <3.5 µg/l [Spec fPL; IDEXX]) was present in one cat. No anemia or liver enzyme elevation was present in this case, and no pancreatitis was visualized on ultrasonographic examination. Medications administered before presentation included glucocorticoids in two cats (one of them owing to suspicion of immune-mediated hemolytic anemia by the referring veterinarian), gastroprotectants (famotidine and/or sucralfate) in 4/6 cats, maropitant in 2/6 cats, and insulin glargine, metronidazole, enrofloxacin, buprenorphine and subcutaneous fluids in 1/6 cat.

Abdominal ultrasound was performed in all six cats. The presence of a discrete, small (from 6 mm up to 1.5 cm at its largest dimension), round-to-oval-shaped, moderately echogenic and homogeneous nodule filling most of the proximal duodenal or pyloroduodenal lumen was noted in all six cats (Figure 1). In one cat, color flow Doppler outlined vessels within the nodule (Figure 2), whereas in another cat, there was no clear evidence of intranodular vessels. Data on color flow Doppler were not available in the other four cats. The visible adjacent pyloroduodenal walls appeared normally layered in 5/6 cases. In one cat, the duodenal wall opposite the nodule was thickened (5 mm) with fewer distinct layers, and the adjacent fat was hyperechoic (Figure 3). In this cat, surgery revealed a 7 mm ulceration of the duodenal wall opposite the polyp. In 2/6 cats, the stomach was fluid-distended, suggestive of decreased gastric emptying. Echogenic fluid in the lumen was at times difficult to distinguish from the margins of the similarly echogenic nodular lesion. For 2/6 cats, the nodular lesion was missed at the initial examination, as the echogenic gastric fluid had similar echogenicity to the lesion. Regional lymph nodes were within normal limits in all cats.

Figure 1

Longitudinal sonogram of a pyloric polyp (between calipers – 0.6 × 1 cm). The uniformly echogenic nodule is partially outlined by the luminal gas. ST = stomach; GB = gall bladder

Figure 2

Pyloric antrum. Color flow Doppler outlines the blood flow within the polyp. The margins of the polyp are not clearly demarcated (arrowheads), as the adjacent ingesta (*) is nearly isoechoic to the nodule. D = duodenum

Figure 3

Transverse sonogram of the proximal duodenal polyp of a 5-year-old cat. The echogenic nodule (between calipers) is filling the lumen. Note the hyperechoic fat (arrows) along the duodenum. The wall facing the nodule was ulcerated on endoscopy, explaining the regional steatitis seen on ultrasound

Laparotomy was performed in all cases but was preceded by upper gastrointestinal endoscopy in two cats. In one of the cases, upper gastrointestinal endoscopy revealed a round, smooth, pedunculated mass encircled by a string foreign body at the junction of the pylorus and duodenum. Endoscopy was unsuccessful at removing the mass and the string; a laparotomy was then performed. In the other case, endoscopy revealed digested blood covering the entire surface of the stomach and a small pedunculated cauliflower-like mass in the duodenum obstructing the duodenal papilla. At surgery, a single pedunculated mass was noted at the junction between the pylorus and duodenum in 5/6 cases. In one case, three polypoid masses were removed from the pyloric antrum. Surgical exploration revealed macroscopic gastrointestinal bleeding in two cases and visible ulceration in three of the remaining cases, including the case with the foreign material. In one case, the location of the ulceration was not reported. In the second case, ulceration and bleeding were noted from the mucosa of the polyps, whereas in the third case, the ulceration was noted on the duodenal mucosa opposite to the polyp. Two cases, including one that underwent endoscopy, had polyps partially covering the duodenal papilla. In all cases, surgery was successful in fully removing the polyps. All but one survived to discharge. This cat had massive blood loss and anemia (hematocrit of 8%) with subsequent cardiac arrest and successful resuscitation at the general practice it was initially admitted to before being referred. The severe blood loss and initial cardiac arrest was the consequence of massive gastrointestinal bleeding due to ulceration of the gastroduodenal polyp. Unfortunately, severe progressive azotemia developed the day after surgery and owners elected euthanasia. The owner declined autopsy. Of the five remaining cases, one was lost to follow-up and four were still alive free of any clinical signs (mean 817 days) at the time of the writing.

In all six cases, the nodules were histologically identified as benign, polypoid proliferative, epithelial lesions with irregular tubules or glands as the predominant arrangement. The four cases whose slides were available for review were ultimately classified as adenomatous polyps, although other terms reported as diagnoses or mentioned in the comments of the six original biopsy reports included polyp, gastric polyp, mucosal epithelial polyp, hyperplastic polyp, gastroduodenal polypoid adenoma and adenomatous hyperplasia.

The four cases available for histologic review had erosion/ulceration associated with the surface of the polyp. In two cases, erosion and ulceration was noted on the adjacent mucosa. One of these two cases also had concurrent ulceration of the polyp.

Mucosa adjacent to the polyp was described histologically in three cases and contained only gastric mucosa in two cases and both gastric and duodenal mucosa in one case.

Discussion

Pyloroduodenal polyps are rare in cats. In a retrospective study including 1311 feline intestinal tumors identified, ⁹ no pyloroduodenal polyps were reported, but 24 cases of polyps or papilloma were described, all of them arising from the large intestine. Unlike previous studies, only one of our patients was related to an Asian breed.^1,4 Similarly to these studies, cats in our study were elderly patients with a mean age of 9.6 years. ⁴

In this study, we report six cases of pyloroduodenal polyps ultrasonographically visualized in cats. To our knowledge, there is no ultrasonographic description of these lesions published in the peer-reviewed veterinary literature. Despite the fact that all ultrasonographic examinations were performed or reviewed by board-certified radiologists, 2/6 polyps were missed during the initial examination. The polyps were retrospectively identified on the still and/or video clips recorded once reviewed by the board certified radiologist on this publication (DP). Pyloroduodenal polyps in cats are easily missed during ultrasonographic examination because their echotexture can mimic normal echogenic ingesta. Therefore, the real incidence of this lesion in cats remains to be established. In this study, 5/6 of the cats had normal duodenal layering and in all the cases the polyps were visualized as a moderately echogenic round-to-oval nodule projecting into the lumen (Figure 1). In our cats, 5/6 of the polyps were single pedunculated nodules visualized near the pylorus or proximal duodenum based on the surgical description. In the last case, three polypoid masses were removed from the pyloric antrum.

It was reported that in the light of the age of the cats, the clinical signs and the presence of an intestinal nodule, pyloroduodenal polyps can be easily mistaken for gastrointestinal neoplasia.^4,5,9 Differential diagnosis for pyloroduodenal nodules or masses in elderly cats include neoplastic lesions such as adenocarcinoma, lymphoma, mast cell tumor, smooth muscle tumor or benign lesions such as granulomatous disease and feline gastrointestinal eosinophilic sclerosing fibroplasia.^9,10 However, most gastrointestinal tumors tend to be poorly echogenic with altered or lost wall layering. Additionally, carcinoma and lymphoma tend to be circumferential, while smooth muscle tumors tend to be exophytic. ⁸ Gastric polyps in dogs have been reported as echogenic nodular projections arising from the gastric mucosal; ² this feature is similar to the one we describe in this study. Lesions of feline gastrointestinal eosinophilic sclerosing fibroplasia was reported to be inhomogeneous with hyperechoic foci. ¹⁰ Because the prognosis of surgically removed pyloroduodenal polyps is excellent, it is important to consider the possibility of pyloroduodenal polyps if a moderately echogenic nodule is filling most of the proximal duodenal or pyloroduodenal lumen.

Despite the fact that pyloroduodenal polyps are considered as a benign process in human and veterinary medicine, it is important to recognize that the clinical signs related to these polyps can, in some cases, lead to severe complications.^3–5,11 Ulceration and/or erosion were observed on the polyp and/or adjacent tissue in 5/6 cases. Therefore, pyloroduodenal polyps in cats can be a source of gastrointestinal blood loss. In our study, acute vomiting compatible with partial gastrointestinal obstruction was the most common presentation. These signs were accompanied by gastrointestinal bleeding in three of the cases. These findings are similar to previous reports.^1,4 One of our cases also had increased bilirubin and the lesion location was compatible with partial or intermittent biliary obstruction. The resolution of the clinical signs after surgery and the long-term follow-up period supports that the polyps were likely the main cause of the initial clinical presentation in this study. Our study is also likely to be overestimating the severity of the clinical signs associated with pyloroduodenal polyps in cats as the polyps were diagnosed only after the cats were presented to a referral center for severe or persistent clinical signs.

A continuum between some subtypes of gastric polyps and neoplasia has been described in human medicine and, in rare instances, in dogs, but similar findings are yet to be investigated in cats.^1,2,11

Given the successful outcome of the majority of these cases, the likelihood of these lesions representing a premalignant status appears low but requires further study. Endoscopic or ultrasonographic rechecks were not available to assess recurrence of the polyps or growth of a new lesion. However, the extended follow-up period without clinical signs supports complete recovery after successful removal of these benign polyps.

The main limitations of this study are the retrospective nature of the study and the small number of cases. The prevalence of pyloroduodenal polyps in cats remains to be determined, and the design of a robust prospective study with recruitment of multiple veterinary centers for an extended enrollment period would be beneficial to assess prevalence and clinical impact of these polyps.

Conclusions

Pyloroduodenal polyps in cats can have subtle ultrasonographic changes and can be mistaken for normal ingesta. When a moderately echogenic and homogeneous nodule filling most of the proximal duodenal or pyloroduodenal lumen is noted on ultrasonographic examination without regional lymphadenopathy, the possibility of a benign pyloroduodenal polyp should be considered, regardless of the severity of the clinical signs. If the polyp can be surgically removed, pyloroduodenal polyps carry an excellent prognosis.