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Radiological Reasoning: Recurrent Right Lower Quadrant Inflammatory Mass

¹ Both authors: Department of Radiology, University of Washington, Harborview Medical Center, 325 Ninth Ave., Box 359728, Seattle, WA 98104-2499.

Received June 20, 2005; accepted after revision July 13, 2005.

 
Address correspondence to M. M. Bittle (mbittle{at}u.washington.edu).

Abstract

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Objective

We discuss the case of a 58-year-old woman who presented with right lower quadrant pain and fever. CT showed a right lower quadrant inflammatory mass presumed to be an appendiceal abscess. The patient underwent open drainage of the mass but failed to return for an interval appendectomy. She returned 23 months later with a recurrent right lower quadrant inflammatory mass treated initially with percutaneous drainage followed by interval appendectomy. The final pathologic diagnosis was mucinous cystadenoma with perforation.

Conclusion

Primary neoplasms of the appendix are uncommon but should be considered in the correct clinical and imaging scenario.

Case History

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First Presentation
A 58-year-old woman presented to an outpatient clinic with a 2-week history of abdominal pain, fever, and constipation. She was transferred to an emergency department for further evaluation. Physical examination revealed a soft abdomen with normal bowel sounds and mild right lower quadrant tenderness and rebound. Laboratory data revealed leukocytosis and urinalysis with 1+ gram-positive rods and cocci. Abdominopelvic CT was performed (Figs. 1A, 1B, and 1C).

View larger version (98K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A —58-year-old woman with initial presentation of right lower quadrant pain. Abdominopelvic CT with oral and IV contrast at initial presentation. CT slice through upper abdomen.

View larger version (113K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B —58-year-old woman with initial presentation of right lower quadrant pain. Abdominopelvic CT with oral and IV contrast at initial presentation. CT slice through upper pelvis.

View larger version (116K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C —58-year-old woman with initial presentation of right lower quadrant pain. Abdominopelvic CT with oral and IV contrast at initial presentation. CT slice through lower pelvis.

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CONTINUING MEDICAL EDUCATION This article is available for 1 hour of Category 1 CME credit. It is free to ARRS members and may be purchased by nonmembers for $10.00. Detailed information including objectives, disclosure information, and how to obtain CME credit can be found at www.arrs.org by selecting AJR Integrative Imaging.

 

Expert (Dr. Bittle)

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I find the clinical presentation to be nonspecific. The infected urine suggests pyelonephritis and the right lower quadrant pain suggests acute appendicitis or diverticulitis. Although I see right hydronephrosis and hydroureter on the CT, the renal parenchymal pattern of enhancement is normal. If pyelonephritis were present, I would have expected to see a striated nephrogram with wedge-shaped areas of focal hypoattenuation secondary to edema or vasospasm. I also do not see perinephric or periureteral fat stranding, findings that are often present in pyelonephritis. The upper and midabdomen are otherwise unremarkable.

Let us proceed now to the right lower quadrant lesion. The masslike abnormality is predominantly cystic and shows heterogeneous peripheral enhancement. The fat stranding surrounding the mass and wall thickening of the cecum and sigmoid colon support an inflammatory or infectious process. The cecal wall thickening is most pronounced in the expected region of the appendiceal orifice. Given the anatomic location of the mass, acute appendicitis with perforation and abscess formation comes to mind and I look for the appendix in the middle of it. Unfortunately, I cannot identify the appendix either within the mass or separately from it, so that introduces some uncertainty about this particular diagnosis. Finding a calcified appendicolith would also be helpful, but I do not see one. No gas is seen within the mass to support abscess, but most appendiceal abscesses will not have gas. In addition, a necrotic neoplasm communicating with bowel might contain gas and could have a similar appearance. The distal right ureter shows stranding and wall thickening, and is compressed by the right lower quadrant mass, explaining the right hydronephrosis and hydroureter.

In summary, the CT findings are best explained by perforated acute appendicitis with focal abscess; this diagnosis fits well with the clinical picture of acute right lower quadrant pain and elevated WBC count. However, since I cannot identify the appendix and the patient's age is slightly older than the typical acute appendicitis patient, I cannot really narrow the differential diagnosis for a right lower quadrant inflammatory mass by imaging alone. Regardless, initial management calls for drainage of the inflammatory mass.

Clinical Management

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Exploratory laparotomy revealed a purulent, loculated abscess cavity. The cecum was viable, but the appendix could not be identified. The abscess cavity was copiously irrigated and drained. Since an appendectomy could not be performed and cecal resection was unnecessary, no pathology specimens were obtained. However, culture of the abscess fluid was positive for Klebsiella pneumoniae, anaerobic gram-negative rods, and anaerobic non-spore forming gram-positive rods. Shortly after discharge, the patient had a normal colonoscopy. The patient was to return in 6 weeks for an interval appendectomy.

Expert (Dr. Bittle)

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The operative findings confirmed appendicitis with perforation and abscess formation, but the failure to identify the appendix at the time of surgery is unexpected and perplexing. An exploratory operation should lead to a pathologic diagnosis based on the examination of tissue. I am concerned that the surgeons treated an infection superimposed on a preexisting appendiceal mass without identifying the underlying pathology. Neoplasms of the appendix such as cystadenoma and cystadeno-carcinoma may present with symptoms related to an infected mucocele. Although much less common, other primary neoplasms of the appendix to consider include colonic-type (nonmucinous) adenocarcinoma, carcinoid tumor, goblet cell carcinoid tumor, and non-Hodgkin's lymphoma. Any of these lesions may cause an obstruction of the appendix that results in appendicitis in much the same way as an appendicolith. The return visit for appendectomy is therefore a key step in the care of this patient.

Commentary

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Abdominal abscesses have a fairly characteristic appearance on CT with central low density and peripheral enhancement. Most have surrounding inflammatory response. Variable amounts of gas are present in only one third of abdominal abscesses [1]. Foley et al. [2] have reported that extraluminal air and moderate or marked periappendiceal inflammatory stranding are statistically significant independent predictors for appendiceal perforation. The identification of an abscess or extraluminal air is a specific but insensitive finding in patients with perforated appendicitis. Moderate or severe periappendiceal inflammatory changes in the mesoappendix and adjacent retroperitoneal fat and a focal defect in the enhancing appendiceal wall are more sensitive but less specific signs. Indeed, care must be taken to avoid the misinterpretation of partial volume averaging as a focal enhancement defect in the appendiceal wall [2]. Pathophysiologically, acute appendicitis results from obstruction of the appendix, most commonly by a stone or tumor. The treatment generally has been surgical removal of the appendix, but nonoperative management and percutaneous drainage of perforated appendicitis with interval appendectomy has been advocated in the surgical literature [3]. Acute management with percutaneous drainage has a few contraindications, including coagulopathy, unsafe access route, and poor patient cooperation [4]. Interval appendectomy is recommended because of the risk of recurrent appendicitis or unrecognized malignancy [5]. The CT findings of recurrent appendicitis are indistinguishable from those of acute appendicitis [6]. Approximately 7% of patients who have appendectomy for acute appendicitis have clinical and histopathologic evidence of one or more previous episodes of appendicitis [7, 8]. The recurrence rate in one large study was 14% (32 of 237) [9], and 16% (4 of 24) in an earlier, smaller study [10]. The risk of unrecognized malignancy is small, present in only 0.5-1% of surgical specimens for appendicitis [11].

Case History

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Second Presentation
The patient returned to the emergency department 23 months after the initial presentation, now complaining of 4 days of recurrent right lower quadrant pain. Physical examination showed mild tenderness with rebound in the right lower quadrant. The WBC count was normal and the urine was clear. Abdominopelvic CT was performed (Fig. 2A and B).

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A —58-year-old woman with recurrent presentation of right lower quadrant pain. Abdominopelvic CT with oral and IV contrast at second presentation, 23 months after initial presentation. CT slice through upper pelvis.

View larger version (126K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B —58-year-old woman with recurrent presentation of right lower quadrant pain. Abdominopelvic CT with oral and IV contrast at second presentation, 23 months after initial presentation. CT slice through lower pelvis.

Top Abstract Case History Computed Tomography Expert (Dr. Bittle) Clinical Management Expert (Dr. Bittle) Commentary Case History Computed Tomography Expert (Dr. Bittle) Clinical Management Expert (Dr. Bittle) Commentary Solution to Question 1 Solution to Question 2 Solution to Question 3 Solution to Question 4 References

Expert (Dr. Bittle)

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The patient's initial CT showed a right lower quadrant inflammatory mass indistinguishable from perforated acute appendicitis with abscess formation. She now returns with a very similar imaging appearance and clinical presentation except that her WBC count is normal. We know she did not undergo interval appendectomy. Although recurrent appendiceal abscess is a consideration, it would be very unusual not to have an accompanying elevation of the WBC in an otherwise healthy woman unless she were on steroids or similar medications. Because of the long duration between presentations (23 months) and the normal laboratory values, I am really suspicious of an underlying mass or neoplasm. Possible sites of origin include the cecum, the appendix, or the right ovary. I favor appendix as the most likely site of origin. A normal-sized right ovary can be identified, eliminating an ovarian tumor as a possible underlying cause.

Clinical Management

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Interventional radiology performed percutaneous drainage of the presumed recurrent appendiceal abscess (Fig. 3). Culture contained Klebsiella, mixed Streptococcus species, mixed anaerobic flora, and presumptive Clostridium species. The patient's symptoms remitted. At the time of interval appendectomy 7 weeks later, a firm inflammatory mass was found adherent to the retroperitoneum, iliac vessels, and right ureter. Extensive adhesions were present in the right lower quadrant. Soft mucoid material also was present. The cecum was devitalized and a right hemicolectomy was performed. The appendix was not identified at the time of surgery, but was found on pathologic sections through the inflammatory mass. The final pathologic diagnosis was mucinous cystadenoma with perforation, mucus extravasation into the appendiceal wall and peritoneum, and serosal reactive changes of localized pseudomyxoma peritonei. The postsurgical course was uneventful and the patient remains asymptomatic.

View larger version (97K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3 —CT with oral and IV contrast through pelvis after percutaneous drain placement.

Expert (Dr. Bittle)

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This case is particularly difficult because I could not find the appendix, but then again neither could the surgeons on two separate occasions. I can find no credible clues to the specific diagnosis on either of the CT scans although as I have indicated, underlying tumor had to be considered from the overall appearances. MDCT coronal reformations improve confidence in visualization of the appendix (whether diseased or normal) and in diagnosis or exclusion of appendicitis and may have been helpful in this case in identifying the appendix [12].

Commentary

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Primary neoplasms of the appendix are uncommon. Approximately 30-50% of such lesions will present with signs and symptoms of acute appendicitis [11]. Pickhardt et al. [11] report that CT is a sensitive technique for detecting the presence of an underlying appendiceal neoplasm in patients with secondary appendicitis. Morphologic changes, such as the presence of appendiceal cystic dilatation and/or a focal soft-tissue mass, were present in the majority of their cases. An appendiceal diameter greater than 15 mm is probably not a specific indicator, but they claim that this finding should also be viewed with suspicion [11].

Older age of the patient may also suggest underlying neoplasm since approximately 69% of patients with acute appendicitis are under age 30 [11]. Preoperative diagnosis of a primary appendiceal tumor is important as it may change the surgical approach (laparoscopic vs open) and the appropriate surgical procedure (appendectomy vs right hemicolectomy). Recognition of this possibility could thus obviate additional surgery and may indeed help guide the appropriate use of percutaneous drainage. However, it is recognized that differentiating complicated appendicitis with perforation and abscess from cystic appendiceal neoplasms at CT is difficult and challenging, as in this case [11]. The importance of clearly communicating to the surgical team the possibility of an underlying neoplasm based on the radiologic findings should be emphasized as a more thorough search may have been beneficial in this case.

The most common primary appendiceal neoplasms are benign and malignant mucinous neoplasms. Mucocele is a generic term used to describe the appearance of mucinous dilatation of the appendix regardless of its cause. Mucoceles may result from such causes as benign or malignant neoplasms, endometriosis, and retention cysts. Simple retention cysts rarely dilate the appendix greater than 2 cm. A neoplastic or nonneoplastic mucocele typically presents with diffuse distention of the appendix with low-density material and, occasionally, curvilinear mural calcifications. Mucinous neoplasms of the appendix typically do not present as acute appendicitis unless secondarily infected since obstruction of the appendiceal lumen occurs slowly over time with little inflammatory response. Secondary infection may complicate both benign and malignant mucinous neoplasms. Irregularity and soft-tissue thickening of the mucocele wall and surrounding inflammatory fat stranding are findings suggestive of malignant mucinous adenocarcinoma. These findings may also be seen with secondary infection, occasionally presenting a diagnostic dilemma. If a malignant mucinous neoplasm is suspected, a right hemicolectomy is indicated rather than simple excision of the appendix (appendectomy). Pseudomyxoma peritonei with intraabdominal gelatinous material may complicate both benign and malignant mucoceles. Increasing abdominal girth may be the initial presenting complaint in a substantial subset of patients with appendiceal mucinous adenocarcinomas due to the development of pseudomyxoma peritonei from mucocele rupture or transmural extension. Preventing spillage intraoperatively is also important to avoid the complication of pseudomyxoma peritonei, which carries a poor prognosis with a 5-year survival rate of 65% when diffuse [13]. Diffuse disease usually requires surgical debulking and omentectomy. Localized pseudomyxoma peritonei, as in the case presented, has a much better prognosis.

Nonmucinous primary neoplasms of the appendix include colonic-type (nonmucinous) adenocarcinoma, carcinoid tumor, goblet cell carcinoid tumor, and non-Hodgkin's lymphoma. Colonic-type neoplasms present as an appendiceal soft-tissue mass and may be locally infiltrative into the periappendiceal fat or adjacent organs. Carcinoid tumors of the appendix are not typically detected directly by imaging due to their small size and location in the distal appendix. Rarely, at presentation, appendiceal carcinoid may be metastatic and a mesenteric mass or liver mass may be encountered. Goblet cell carcinoid tumors are a low-grade malignancy, intermediate between classic carcinoid and adenocarcinoma, with an infiltrative growth pattern causing circumferential wall thickening. Lymphoma manifests as marked enlargement of the appendix with diffuse wall thickening and relative maintenance of its vermiform shape.

QUESTION 1 In febrile patients presenting with right lower quadrant pain and leukocytosis, are oral and IV contrast indicated when evaluating the abdomen and pelvis with CT? NEITHER type of contrast administration is indicated because calcifications may be difficult to identify in the presence of contrast. ONLY oral contrast is indicated because IV contrast increases the risk to the patient without improving visualization of likely abnormalities. ONLY IV contrast is indicated because oral contrast filling the appendix might obscure an appendicolith. BOTH are indicated because a dilated, obstructed appendix will be easier to find with oral contrast, and an abscess is easier to find with IV contrast. QUESTION 2 A primary appendiceal neoplasm underlying acute appendicitis would be suggested by which imaging finding? A dilated appendix. Appendiceal soft-tissue mass. Inflammation surrounding the appendix. Calcifications in the appendix. QUESTION 3 Which is the most likely explanation for right hydronephrosis and right hydroureter that occur in the setting of acute appendicitis with perforation and abscess formation? Right ureteral obstruction caused by an intraluminal lesion. Concurrent pyelonephritis involving the right kidney. Underlying mucinous appendiceal tumor with direct engulfment of the ureter. Extrinsic compression with periureteral inflammation. QUESTION 4 Which statement is TRUE regarding recurrent appendicitis? Fewer than 1% of patients who have appendectomy for appendicitis will have evidence of previous appendicitis. CT findings of recurrent appendicitis are indistinguishable from those of acute appendicitis. The recurrence rate after nonoperative percutaneous drainage for acute appendicitis is less than 5%. Unrecognized malignancy is found in over 5% of surgical specimens removed for appendicitis.

 

In women, it is essential to identify the right ovary to exclude adnexal pathology such as cystic ovarian neoplasm, tuboovarian abscess, and hydrosalpinx. Finally, presenting symptoms of a primary appendiceal neoplasm may be related to obstruction of the right ureter. Although uncommon, primary neoplasms of the appendix should be considered in the correct clinical and imaging scenario.

Solution to Question 1

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The use of IV and oral contrast in patients with right lower quadrant pain is an interesting question and one that relies heavily on the clinical history and physical examination, since the differential diagnosis of the clinical scenario is quite extensive. The presence or absence of hematuria is an important consideration. Hematuria can be seen with urinary tract calculi or secondary to periureteral inflammation and infection resulting from acute appendicitis. IV contrast in the kidney and ureter would obscure urinary tract calculi and should not be used if this is the main clinical question to be answered. The clinical information presented in the question suggests that infection is the main clinical question to be answered. Option A is not the best response.

While there is an acknowledged risk to the patient from the IV administration of iodinated contrast medium, this risk is generally acceptable when low osmolar contrast is used. The clinical scenario suggests that possible infection is an important consideration. Peripheral enhancement of a fluid collection or enhancement of phlegmonous tissue will aid in the diagnosis of an abscess and would help differentiate infected fluid from simple fluid. Option B is not the best response.

If an appendicolith is present in the setting of acute appendicitis, the appendix will be obstructed, and cannot fill with oral contrast. Complete filling of the appendix with oral contrast is actually an indication that acute appendicitis is NOT present. Option C is not the best response.

The presence of fever and elevated WBC count may direct the use of IV and oral contrast. While fever and elevated WBC count could be seen with pyelonephritis, another diagnosis to consider is acute appendicitis. In this case, oral contrast will opacify bowel and help delineate a dilated and unopacified appendix from the sometimes confusing appearance of unopacified bowel. In addition, an appendix filled with oral contrast essentially excludes acute appendicitis. The use of IV contrast is particularly helpful in the setting of perforated appendicitis and abscess formation. In conclusion, provided with the history of fever and elevated WBC count, both oral and IV contrast would be indicated in the clinical scenario described. Option D is the best response.

Solution to Question 2

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A dilated appendix occurs with acute appendicitis, but will also be seen with primary tumors of the appendix. An appendiceal mucocele typically presents with diffuse distention of the appendix with low-density material. Lymphoma of the appendix will show an enlarged appendix with diffuse wall thickening and maintenance of its vermiform shape. Goblet cell tumors have an infiltrative growth pattern resulting in circumferential wall thickening. Option A is not the best response.

An appendiceal soft-tissue mass may be seen with colonic-type primary appendiceal neoplasms. They may also be locally infiltrative into the periappendiceal fat and adjacent organs. Appendiceal carcinoid tumors are usually small and distal in the appendix and typically not directly detected during imaging. Option B is the best response.

Inflammation surrounding the appendix can be seen with primary tumors of the appendix such as a colonic-type with local infiltrative growth. More often, however, it is seen with obstruction of the appendix and secondary infection from any neoplastic or nonneoplastic cause such as an appendicolith or mucinous neoplasms. Option C is not the best response.

Calcifications in the appendix are often seen secondary to an appendicolith, which may be an incidental finding in some patients. Curvilinear mural calcifications also are associated with neoplastic and nonneoplastic mucoceles of the appendix. Option D is not the best response.

Solution to Question 3

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Hydronephrosis and hydroureter are caused by ureteral obstruction. In general, the most common intraluminal cause would be an obstructing urinary tract calculus, with an intrinsic urothelial malignancy being less likely. However, neither one of these lesions is associated with appendicitis. Option A is not the best response.

Pyelonephritis may present with right flank pain that radiates to the right lower quadrant, simulating acute appendicitis. While pyuria may occur in acute appendicitis as a result of periureteral inflammation, pyelonephritis is not associated with acute appendicitis. Option B is not the best response.

Mucinous tumors are the most common type of primary tumors of the appendix. They typically occur as cystic masses that may affect adjacent structures by mass effect but not by surrounding and engulfing them. Option C is not the best response.

Right ureteral obstruction may result from extrinsic compression. As in the case discussed here, perforation of an acutely inflamed appendix results in abscess formation. The right lower quadrant abscess may surround and obstruct the distal ureter, leading to hydronephrosis and hydroureter. Periureteral inflammation may also result in pyuria and hematuria, which may confuse the clinical picture. Option D is the best response.

Solution to Question 4

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Clinical and histopathologic evidence of one or more previous episodes of appendicitis may be found in as many as 7% of appendectomy specimens for appendicitis, suggesting that recurrent appendicitis is not rare. Option A is not the best response.

The CT findings of acute appendicitis and of recurrent appendicitis are indistinguishable. These include an enlarged, fluid-filled appendix, periappendiceal fat stranding, and frank abscess formation. Option B is the best response.

The recurrence rate for acute appendicitis treated with nonoperative percutaneous drainage is approximately 14% in large series. Elective appendectomy generally is recommended after nonoperative management of acute appendicitis. Option C is not the best response.

Unrecognized malignancy is found in 0.5–1% of surgical specimens for acute appendicitis; 30–50% of patients with a primary appendiceal malignancy will present similarly to those with typical acute appendicitis. Option D is not the best response.

References

Top Abstract Case History Computed Tomography Expert (Dr. Bittle) Clinical Management Expert (Dr. Bittle) Commentary Case History Computed Tomography Expert (Dr. Bittle) Clinical Management Expert (Dr. Bittle) Commentary Solution to Question 1 Solution to Question 2 Solution to Question 3 Solution to Question 4 References

 

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				C. C. Roberts, M. M. Bittle, and F. S. Chew Imaging Evaluation of Right Lower Quadrant Pain: Self-Assessment Module Am. J. Roentgenol., September 1, 2006; 187(3_Supplement): S476 - S479. [Abstract] [Full Text] [PDF]

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