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INTRODUCTION AND IMPORTANCE: Malignant peripheral nerve sheath tumor is an aggressive tumor that arises from peripheral nerves. Frequently associated with neurofibromatosis, its common localization is in the extremities, trunk (with paravertebral regions), neck and head. Some cases have been found in the pelvis or uterus. In this case report we illustrate one of the rarest localization of this type of tumor in the ischiorectal fossa, with the full recovery of the patient after surgical excision and radiotherapy. CASE PRESENTATION: A 61-year-old woman showed a lump near the anus which was initially diagnosed as a lipoma of the right ischiorectal fossa, by Computed Tomography scan. The tumor was completely removed with a minimal skin incision, and the patient had a complete recovery. Only the pathological examination determined the diagnosis of malignant peripheral nerve sheath tumor, in this unusual localization. In consideration of its high aggressiveness the patient underwent radiotherapy. After more than two years of follow-up there is no sign of recurrence. DISCUSSION: In sites far from branches of nerves, malignant peripheral nerve sheath tumors can be considered episodic. Ischiorectal fossa is a rare localization, and the differential diagnosis from benign mesenchymal cell tumors can be challenging. When possible, a biopsy should be performed before surgery. CONCLUSION: Surgical excision of tumors in ischiorectal fossa should be always complete, in consideration of possible histological surprise.

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Emphysematous cystitis is an extremely rare, complicated urinary tract infection with the presence of gas in the bladder wall and lumen caused by gas-producing bacterial infections. A 7-year-old spayed female pomeranian dog was presented with a 3-day history of hematuria and pollakiuria (case 1), and a 9-year-old spayed female jindo dog was presented with a 4-day history of intermittent hematuria (case 2). Imaging modalities, including radiography, ultrasonography, and computed tomography, and bacterial culture tests were used for the diagnosis. Emphysematous cystitis due to Escherichia coli infection with the extension of gas into multiple locations was identified in both cases. Based on the results of antibiotic susceptibility testing, systemic antibiotics were initiated. Both animals had an excellent response to antibiotic treatment, and the clinical signs of the gas collection were completely resolved within ~1 month after treatment initiation. This response was sustained without recurrence in the follow-up period. This case report describes clinical details of extremely rare canine cases of emphysematous cystitis with the extension of gas into multiple locations and evaluates the clinical efficacy of antibiotic therapy.

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The anatomic variations of the perineal arteries and nerves are studied in the dog. The aim of the study is to provide a more detailed understanding of the blood supply and innervation of the perineal region, providing detailed information on the perineal arteries and nerve distribution and their variability in male and female dogs. The study used 232 pelvic halves from 116 adult dogs and analysed the differences using the chi-squared test. The results showed that the presumptive model for perineal artery distribution described in N.A.V. was observed in 46% of the specimens. Additionally, a dorsal perineal artery "long type" was found in 13% of the dogs, and a perineal trunk was present in 41% of the dogs. In the study, there was no variation in perineal nerve distribution, and it was found that the perineal nerve did not run together with the dorsal perineal artery when it was the "short type" as described in the presumptive model for perineal artery distribution. Instead, it always followed the route of the dorsal perineal artery "long type" and the perineal trunk when they were present. The findings of the study may be useful for veterinary surgeons when approaching the perineal region in dogs.

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Lipoblastoma is a relatively rare tumor that occurs in infancy and early childhood which arises from embryonic fat. It occurs mostly in trunk and extremities, but abdomen and pelvic lipoblastomas are rare. It presents as a mass with or without mass effect. Computed tomography/magnetic resonance imaging of the abdomen with pelvis is the investigation of choice. We present two cases of pelvic lipoblastoma with extension in ischiorectal fossa and the intra-abdominal lipoblastoma which were excised completely by laparoscopy. We are reporting these cases because of rarity of the disease and feasibility of complete laparoscopic excision.

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BACKGROUND: In the anal sphincter complex, the intersphincteric space between the internal and external sphincters is the only conventionally recognized pathway for the spread of sepsis. However, there is another unrecognized space discovered on MRI, the "outer-sphincteric space", between the external anal sphincter and its lateral fascia along which pus can spread. An abscess in the intersphincteric space is easily drained into the rectum via the transanal route and is more likely to spread into the supralevator space. Conversely, an abscess in the outer-sphincteric space is difficult to drain transanally into the rectum and is more likely to become a transsphincteric abscess/fistula. METHODS: The MRIs of anal fistula patients operated over four years on intersphincteric abscesses were analyzed. The pattern of spread into the ischiorectal fossa and/or supralevator space and ease of drainage into the rectum through the transanal route were studied. RESULTS: Thirty-six patients were operated on to drain their intersphincteric abscesses through the anal canal. Two distinct patterns were noted. Twenty patients had abscesses in the intersphincteric space, which were easily drained into the rectum. Of them, 6/20 had supralevator extension, while only 1/20 had spread to the ischiorectal fossa. In 16/36 patients, the abscess was in the outer-sphincteric space and could not be drained into the rectum. In 9/16 of these patients, pus spread into the ischiorectal fossa but supralevator spread did not happen in any patient. CONCLUSION: Apart from the intersphincteric space, there is perhaps another unrecognized anatomical space - the outer-sphincteric space - discovered on MRI, through which pus can spread in anal fistulas or abscesses.

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BACKGROUND: As experience with anal fistula imaging (MRI) has increased, new pathways of fistula extension have been identified. A recently described pathway is the  'outer-sphincteric space' present between the external anal sphincter and its covering outer fascia. A new type of complex fistula is being described which is present in the outer-sphincteric space and continues superiorly along the lateral border of the external anal sphincter to the infero-lateral surface of the puborectalis and levator-ani. In effect, these outer-sphincteric fistulas are at the roof of the ischiorectal fossa inside the levator muscle (RIFIL). These fistulas are not transsphincteric fistulas as they remain inside the levator muscle and do not enter the ischiorectal fossa. METHODS: The MRI scans of consecutive anal fistula patients operated over the last two years were analyzed retrospectively. RESULTS: Of 419 operated fistula patients analyzed, 42(10%) had RIFIL and 377 non-RIFIL fistulas. Compared to non-RIFIL fistulas, there were significantly more recurrent, multiple tracts, horseshoe, supralevator, and suprasphincteric fistulas in the RIFIL group. RIFIL fistulas were significantly more complex than non-RIFIL fistulas(85.7% vs 38.5%, p < 0.00001) and the surgery failure rate was also significantly higher in the RIFIL group (30.6%) than in the non-RIFIL fistula (7.2%) group(p = 0.0001). CONCLUSION: RIFIL are highly complex fistulas. Proper diagnosis by MRI, surgical access, and subsequent management of these fistulas is quite challenging and they are associated with poor prognosis. Missing their diagnosis would lead to higher recurrence rate. These have not been described previously and were perhaps confused with high transsphincteric infralevator fistulas in ischiorectal fossa.

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INTRODUCTION AND IMPORTANCE: Colorectal cancer is one of the most common cancers both nationally and internationally. It commonly metastases to local lymph nodes, liver and lungs, with few reported cases of rare sites of metastasis such as adrenal glands, breast and skin. CASE PRESENTATION: We report a 55-year-old-female admitted as case of large bowel obstruction and unintentional weight loss. Computed tomography scan of chest, abdomen and pelvis (CT CAP) showed sigmoid colon circumferential thickening with three lesions in the right hemi-liver. A laparoscopic diverting ileostomy followed by a colonoscopy showed a sigmoidal mass consistent with adenocarcinoma on histopathology. Hence, she received neoadjuvant chemotherapy followed by hepatectomy for the liver metastasis. Post-operatively CT CAP showed a newly developed right ischiorectal fossa (IRF) nodule along with newly developed porta hepatis lymph node. PET scan showed uptake in these two new lesions. Therefore, the patient underwent resection of the primary tumor, porta hepatis lymph node and right ischiorectal fossa nodule excision. The histopathology of the primary tumor came as moderately differentiated adenocarcinoma with both ischiorectal lesion and the porta hepatis nodule being positive for metastatic disease. CLINICAL DISCUSSION & CONCLUSION: Ischiorectal fossa tumors are extremely rare with the majority being benign in origin. Nevertheless, the possibility of metastasis is there with no clear explanation regarding the pathway of how the metastatic cells can reach the IRF. Pre-operative diagnosis is important to determine the appropriate approach particularly if the mass is thought to be malignant. Further larger studies are needed to understand the pathway of metastasis to IRF.

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Cellular angiofibroma is a recently described rare benign soft-tissue tumor more commonly presenting in middle-aged women, often mimicking malignancy. The vulva is most common location. Complete local excision is the best curative treatment and usually there is no recurrence after surgery. We describe a 49-year-old woman with a painless tumor in the left ischiorectal fossa. It was a random finding in a routine computed tomography (CT) scan after resection of ear melanoma 3 years previously. Ultrasonography showed a solid mass, and further magnetic resonance imaging (MRI) suggested a rhabdomyosarcoma. Altogether, these findings indicated malignant disease. An uncomplicated simple excision of the tumor was done in the operating theatre. The mass measured 7×5×5 cm and the histopathological examination found that it was a cellular angiofibroma, a benign lesion. There were no postoperative complications. This case report highlights the need for multidisciplinary team management of rare tumors such as cellular angiofibromas.

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Prostate cancer is the most common noncutaneous malignancy in American men. Its lymphatic drainage is very well established throughout literature. We report the case of a 72-year-old Caucasian male with elevated serum prostate-specific antigen and biopsy-confirmed high-risk prostate cancer who underwent multiparametric magnetic resonance imaging (MRI) for staging and treatment planning. The imaging revealed suspicious lymph nodes in the left ischiorectal and right obturator fossae that were biopsy confirmed as metastatic prostate adenocarcinoma. Herein, we present the divergence from the well-established lymphatic drainage of prostate cancer and the role of MRI in detecting this prostate cancer site of spread.

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BACKGROUND: The aim of this study was to explore the impact of including or excluding the ischiorectal fossa (IRF) within the clinical target volume during neoadjuvant chemoradiotherapy (NCRT) using intensity modulated radiotherapy, in locally advanced lower rectal cancer (LALRC). METHODS: We retrospectively analysed the data of 220 LALRC patients who received NCRT followed by abdominoperineal resection between January 2009 and January 2015. Six patients were excluded because of loss to follow-up, 90 patients received IRF irradiation (IRF group) while 124 patients did not (NIRF group). Survival, patterns of recurrence, and treatment toxicities were compared between the two groups. RESULTS: Overall, patient/treatment variables were well balanced except for surgical technique. Perineal wound complications in the IRF and NIRF groups, were 40.0 and 24.2%, respectively (p = 0.010); corresponding 3-year perineal recurrence rates, local recurrence free survival, overall survival, and distant relapse free survival were 4.4% vs. 2.4% (p = 0.670), 88.1% vs. 95.0% (p = 0.079), 82.6% vs. 88.4% (p = 0.087), and 61.9% vs. 81.0% (p = 0.026), respectively. Multivariate analyses demonstrated the following factors to be significantly related to perineal wound complications: irradiation of the IRF (odds ratio [OR] 2.892, p = 0.002), anaemia (OR 3.776, p = 0.010), operation duration > 180 min (OR 2.486, p = 0.007), and interval between radiotherapy and surgery > 8 weeks (OR 2.400, p = 0.010). CONCLUSIONS: Exclusion of the IRF from the clinical target volume during NCRT using intensity-modulated radiotherapy in LALRC could lower the incidence of perineal wound complications after abdominoperineal resection, without compromising oncological outcomes.

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PURPOSE: To review the pertinent anatomy and the imaging features of common and uncommon benign and malignant neoplasms and masses of the ischiorectal fossa. RESULTS: The ischiorectal or ischioanal fossa is the largest space in the anorectal region. The benign neoplasms that develop in the ischiorectal originate from the different components that forms the fossa including vascular tumors such as aggressive angiomyxoma or hemangioma; neural tumors as plexiform neurofibroma or schwannoma; fat tumors as lipoma; skin/skin appendages tumors as hidradenoma papilliferum; smooth or skeletal muscle tumors as solitary fibrous tumor. The malignant neoplasms that develop in the ischiorectal fossa also originate from different components that forms the fossa including vascular tumors such as angiosarcoma, neural tumors as malignant granular cell tumor and malignant peripheral nerve sheath tumor; fat tumors as liposarcoma; smooth or skeletal muscle tumors as leiomyosarcoma, rhabdomyosarcoma, malignant PEComa, or undifferentiated pleomorphic sarcoma. Additionally, the ischiorectal fossa can also harbor secondary hematogenous metastases and be affected by direct invasion from neoplasms of adjacent pelvic organs and structures. Furthermore, other miscellaneous masses can occur in the ischiorectal fossa including congenital and developmental lesions, and inflammatory and infectious processes. CONCLUSION: Knowledge of the anatomy, and the spectrum of imaging findings of common and uncommon benign and malignant neoplasms of the ischiorectal fossa is crucial for the radiologists during interpretation of images allowing them to make contributions to the diagnosis and better patient management.

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BACKGROUND: A solitary fibrous tumor (SFT) is a rare mesenchymal tumor that occurs mostly in pleural sites, and an SFT occurring in the ischiorectal fossa is extremely rare. Because of the rarity, there are few reports detailing an SFT in the ischiorectal fossa. CASE PRESENTATION: A pararectal tumor was incidentally found in a 42-year-old man during a routine medical examination. The patient had no symptoms and no previous medical history. In the physical examination, a smooth-margined and hard elastic mass was felt, and in a digital rectal examination, the rectal mucosa appeared normal. A computed tomography (CT) scan showed a 5-cm, well-defined, solid mass in the left ischiorectal fossa. Contrast-enhanced CT in the early phase showed intense heterogeneous enhancement that persisted during the delayed phase. T2-weighted images of magnetic resonance imaging yielded heterogeneous intermediate and low signal intensity. Intense arterial enhancement suggested a hypervascular nature, and persistent delayed enhancement and low signal bands on T2-weighted images suggested a fibrous component of the mass. An SFT was suspected. Most SFTs are benign but have malignant potential. Our patient did not hope for surgery if the tumor was benign; therefore, an ultrasound-guided transperineal core needle biopsy was performed to decide on a treatment strategy. Microscopic examination showed tumor cells appearing as spindle and fibroblast-like cells within a collagenous stroma. Immunohistochemistry identified CD34 and vimentin, supporting the diagnosis of an SFT. The patient consented to excision of the mass. He was placed in a prone jackknife position, and the tumor was removed transperineally using a posterior approach (modified Kraske procedure). The levator ani muscle, external sphincter muscles, and rectum were not involved and separated from the tumor. The tumor was successfully resected en bloc with no complications. Five uneventful days post surgery, the patient was discharged. There was no local recurrence during the year following surgery. CONCLUSION: Imaging findings reflect the tissue characterization such as hypervascularity and fibrous nature of SFTs. We have presented a rare case of an SFT in the ischiorectal fossa with useful imaging findings for diagnosis, treatment strategy, and successful surgical removal using a posterior approach.

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INTRODUCTION: Peri-anal fistulae commonly present with collections requiring surgical intervention. The most common cause of a peri-anal mass is abscess formation secondary to anal gland sepsis. In certain patient groups such as those over 65 or with atypical presenting symptoms there are other important considerations. PRESENTATION OF CASE: A 70-year old male was referred by his general practitioner with symptoms of obstructed defaecation and a palpable mass in the ischiorectal fossa. He had previously undergone three operations for complex peri-anal fistulae in another hospital. Due to the previous history of surgery, seroma formation was considered and computed tomography guided drainage of the lesion was performed unsuccessfully. Given symptoms of obstructed defecation and need for histological diagnosis excision was undertaken. The approach was through a right pararectal incision over the bulk of the mass. Skin and pararectal tissue were divided revealing a mucinous lesion with multiple lobules adherent to pararectal tissue. Following histopathological examination a diagnosis of low grade mucinous neoplasm was made. DISCUSSION: Primary mucinous neoplasm in the ischiorectal fossa is very rare. Diagnostic criteria for adenocarcinoma arising from perianal fistulae have previously been established by Rosser et al. but this lesion does not fall into this category. It is categorised as a mucinous cystic neoplasm of uncertain malignant potential. The differential diagnoses are discussed. CONCLUSION: Consideration should be given to a range of pathologies in cases of atypical peri-anal masses.

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Solitary fibrous tumor (SFT) is a rare neoplasm, which is usually presented as a pleural based mass, but can also occur in unusual locations based on its mesenchymal origin. However, the radiologic features of SFT occurred in the ischiorectal fossa have been rarely reported. In this case, we describe the MRI findings in a case of a SFT involving the ischiorectal fossa of a 36-year-old man. The tumor appeared as homogeneous iso-signal intensity relative to the adjacent muscle on T1 weighted images, a mixed high signal intensity on the T2 weighted images, and heterogeneous enhancement following the administration of the contrast material.

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Aggressive angiomyxoma is a rare soft tissue tumor associated with high risk of local recurrence but lacks metastatic potential. This tumor arise from soft tissue of the perineum or lower pelvis, and affect predominantly yonug women. Aggressive angiomyxoma should be distinguished from more common benign and malignant tumor or tumor like conditions of the pelvic soft part. We report a case of an ususual angiomyxoma in ischiorectal fossa with a brief review of the literature.

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We report a case of aggressive angiomyxoma in ischiorectal fossa of a 39-year-old women. The tumor is characterized by relatively large size(13 x 11 cm), grossly gelatinous appearance and locally infiltrative nature. Microscopically, it consists of many variable sized blood vessels and spindle or stellate cells widely separated in myxoid or collagenous stroma. Immunohistochemical stains reveal that the tumor cells are strongly positive for actin and desmin. Electron microscopic findings are that of a few cells dispersed in abundant intercellular substance and collagen bundles. These cells form irregular cytoplasmic process without basal lamina and contain endoplasmic reticulum having cistern.

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