Peritoneal Pseudocysts - Aetiology, Imaging Appearances and Natural History

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1 Peritoneal Pseudocysts - Aetiology, Imaging Appearances and Natural History Poster No.: C-0663 Congress: ECR 2012 Type: Educational Exhibit Authors: N. Bharwani, M. Crofton; London/UK Keywords: Cysts, Drainage, Diagnostic procedure, Ultrasound, MR, CT, Genital / Reproductive system female DOI: /ecr2012/C-0663 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 48

2 Learning objectives To discuss the aetiology and pathophysiology of peritoneal pseudocysts (PPC). To illustrate the multi-modality imaging appearances of these benign lesions. To appreciate the potential management options and the role of imaging in treatment and follow-up. Images for this section: Fig. 14: Figure 14. Gray scale ultrasound images demonstrating an ovoid peritoneal pseudocyst in the right adnexa (black arrow) lying adjacent to the uterus. A normal right ovary is identified separate to the lesion (white arrow). Appearances mimic those of a para-ovarian cyst. Page 2 of 48

3 Fig. 5: Figure 5. Coronal T2-weighted MRI demonstrating bilateral peritoneal pseudocysts (black arrows) in a pre-menopausal female. The normal left ovary is shown on the image (white arrow) and a normal right ovary was identified lying adjacent to the right sided pseudocyst on an other image. Page 3 of 48

4 Fig. 10: Figure 10. Post-constrast axial CT through the pelvis demonstrates extensive fluid in both adnexal regions that conforms to the contours of adjacent structures (black arrows) in keeping with a peritoneal pseudocyst. Thin enhancing septae are seen to traverse the fluid (black arrowheads). * = Uterus. Page 4 of 48

5 Fig. 17: Figure year old female with previous proctocolectomy and pouch formation. (a) Initial ultrasound performed during acute presentation with pelvic discomfort and abdominal distention shows a large pelvic fluid collection with a normal right ovary identified on the periphery. The fluid collection conforms to the contour of the pelvic viscera in keeping with a peritoneal pseudocyst (PPC). (b) Following ultrasoundguided drainage, there is no significant fluid identified in the pelvis. The normal right ovary is identified again. (c) 2 months following drainage the patient re-attended for followup imaging which showed re-accumulation of fluid around a normal right ovary. The patient was asymptomatic at this point. (d) The patient re-presented for routine followup one year after the initial drainage and the peritoneal pseudocyst was noted to have recurred (the ovary was identified separately to the collection). As the patient remained asymptomatic, there was no further intervention. (e) 2months later the patient underwent further ultrasound which showed a spontaneous reduction in the size of the PPC. (f) Further imaging at an interval of one year showed the PPC starting to re-accumulate. White arrow = Right Ovary. Page 5 of 48

6 Background Peritoneal pseudocysts (PPCs) are also known as peritoneal inclusion cysts, multilocular inclusion cysts, multicystic mesothelioma, inflammatory cysts of the peritoneum, postoperative peritoneal cysts and entrapped ovarian cysts. They are benign mesotheliallined cysts of the abdomino-pelvic cavity which typically occur in women of reproductive age. They can often appear complex on imaging mimicking a cystic ovarian malignancy and can therefore present a diagnostic challenge for clinicians and radiologists. When evaluating a cystic adnexal mass in these young women, it is important for the radiologist to consider non-ovarian disease processes because misdiagnosis can significantly affect patient management. One should assess the anatomical location of the mass, it's relationship to the ovaries and the morphological appearance of the ovaries if they are identified separately. In addition, imaging findings should be evaluated taking into account the patient's clinical history. PPCs often present in patients with a clinical history of prior pelvic surgery, inflammation or endometriosis and typical imaging appearances that should alert the reading radiologist to their benign nature. The correct diagnosis allows conservative management, avoiding unnecessary surgery. We will describe and illustrate the typical multimodality imaging appearances of this benign entity. Long term follow-up in 8 of our cohort of 11 patients provides an insight into the natural history of PPCs. Images for this section: Page 6 of 48

7 Fig. 3: Figure 3. Gray scale ultrasound image demonstrating a small triangular septated fluid collection (black arrow) that does not have a true cyst wall in the left adnexal region. A normal appearing left ovary is identified adjacent to the fluid (white arrow) and is noted to contain a single follicle (black arrowhead). Page 7 of 48

8 Fig. 7: Figure 7. Gray scale ultrasound demonstrating a septated anechoic irregular fluid collection in the left adnexa that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst (black arrows). The left ovary is identified adjacent to the left pelvic side wall (white arrow). Page 8 of 48

9 Fig. 16: Figure 16. The complex left adnexal mass with enhancing thickened septations (black arrows) demonstrated on this post-contrast coronal T1-weighted fat suppressed MR image could easily be mistaken for a primary ovarian malignancy however a morphologically normal left ovary was identified separately on an adjacent section. Page 9 of 48

10 Imaging findings OR Procedure details Clinical Presentation Peritoneal inclusion cysts occur almost exclusively in pre-menopausal women (typically in the third and fourth decade of life (1)), with active ovaries, pelvic adhesions, and impaired absorption of peritoneal fluid, which leads to formation of fluid-filled cysts that conform to the shape of the peritoneal cavity (2-6). The majority of patients come to clinical attention with complaints of chronic or intermittent lower abdominal and/or pelvic pain. Other signs and symptoms include abdominal distention, tenderness, a palpable mass, dyspareunia, constipation and urinary hesitancy and frequency (7;8). Women often have a history of prior pelvic surgery or intra-peritoneal inflammation (most commonly endometriosis, pelvic inflammatory disease or inflammatory bowel disease) (1;8). The duration of symptoms ranges from days to months prior to presentation (7) and in those with previous surgery, the interval between original surgery and the detection of the PPC ranges from 6 months to 20 years (9). With the increased availability of cross-sectional imaging, more PPCs are being discovered incidentally and it is important to correctly identify them as benign entities and avoid anxiety for the patient and unnecessary surgical intervention. They are also occasionally discovered incidentally at surgery and laparoscopy. Pathophysiology The peritoneum is a thin serosal membrane that either partially or completely covers the visceral organs of the abdomen and pelvis. It plays an important role in fluid and lymph reabsorption; failure of this process can cause fluid to accumulate in the peritoneal cavity. PPCs tend to arise in female patients with active ovaries in whom there has been a previous peritoneal insult resulting in failure of absorption and adhesion formation (2-6). In these patients there is accumulation of fluid secreted by the ovarian stroma which is contained by peritoneal adhesions giving rise to loculated fluid collections which appear to conform to the peritoneal space and surrounding viscera. The ovarian origin of the fluid is supported by studies which have shown higher concentrations of ovarian hormones in the peritoneal fluid than in plasma (10;11). Pathologically these cysts have been shown to be adherent to the surface of the ovaries but did not involve the ovarian parenchyma (12). However, the aetiology and nature of the disease process are not well understood and continue to be debated (1). Multimodality Imaging Findings Page 10 of 48

11 As with the majority of gynaecological pathology, trans-abdominal and/or trans-vaginal ultrasound (US) are the first-line imaging modality. US can be employed in the detection, diagnosis, follow-up and image-guided treatment of PPCs. Magnetic resonance imaging (MRI) is the most useful second-line modality in problematic cases due to its high soft tissue resolution and multidimensional imaging capabilities. MRI eloquently delineates female pelvic anatomy and aids characterisation of pelvic masses. Contrast-enhanced images demarcate the uterus, adnexa, and pelvic sidewalls from the irregular walls created by peritoneal adhesions (3;13). PPC can be identified on CT and studies have shown CT to be superior to US in defining cyst borders however CT is overall non-diagnostic for PPC due to the limited soft tissue resolution in the pelvis (14). CT can be useful in identifying an ovarian malignancy and differentiating from benign PPCs by demonstrating enhancing solid components within the lesion, the presence of calcification (an atypical finding in PPCs (15;16)), nodal disease, peritoneal deposits and ascites. It is important not to confuse the enhancing ipsilateral ovary for a solid enhancing nodule. Typically, PPCs are multiseptated, cystic structures that have an intimate anatomic association with the uterus and ovaries. The pseudocyst walls are outlined by the pelvic side walls, uterus and loops of bowel, with a normal ovary located within the cyst. On US, the fluid within the cysts is generally anechoic, but PPCs may contain echoes from debris or haemorrhage (2). On MRI, PPCs typically have signal characteristics in keeping with fluid (high signal intensity (SI) on T2-weighted imaging and low SI on T1weighted images); while CT features are in keeping with those of serous fluid. When complicated by haemorrhage, PPCs will return high SI on T1-weighted images (Figure 1) and the CT attenuation is higher than that of simple fluid. Fig. 1: Figure 1. (a) Gray scale ultrasound, (b) axial T2-weighted MRI and (c) axial fat saturated post-contrast T1-weighted MRI through a left adnexal peritoneal pseudocyst (black arrows). The PPC appears anechoic on ultrasound however the contents return high signal intensity on the T1-weighted fat saturdated images in keeping with haemorrhage. The morphologically normal left ovary is seen on the periphery (which arrows). The patient has had a previous right iliac fossa renal transplant (*). Page 11 of 48

12 References: N. Bharwani; London, UNITED KINGDOM The number and complexity of septations, as well as the size of the cyst locules, are variable (14). Some PPCs have a few incomplete septations, while others have innumerable septations of variable thickness (Figure 2, Figure 3, Figure 4 and Figure 5). At colour Doppler US, low-resistance flow may be seen within the septations, a result of vessels running in mesothelial tissue (Figure 6) (2). On CT and MRI cyst walls can demonstrate enhancement with IV contrast secondary to the vascular component of the septae. Fig. 2: Figure 2. Gray scale ultrasound image demonstrating a septated fluid collection that conforms to the contours of the peritoneal cavity with a normal appearing right ovary identified eccentrically (white arrow). References: N. Bharwani; London, UNITED KINGDOM Page 12 of 48

13 Fig. 3: Figure 3. Gray scale ultrasound image demonstrating a small triangular septated fluid collection (black arrow) that does not have a true cyst wall in the left adnexal region. A normal appearing left ovary is identified adjacent to the fluid (white arrow) and is noted to contain a single follicle (black arrowhead). References: N. Bharwani; London, UNITED KINGDOM Page 13 of 48

14 Fig. 4: Figure 4. Gray scale ultrasound image demonstrating an irregular septated fluid collection in the left adnexa that conforms to the surrounding structures. A normal appearing left ovary is identified adjacent to the fluid (white arrow). References: N. Bharwani; London, UNITED KINGDOM Page 14 of 48

15 Fig. 5: Figure 5. Coronal T2-weighted MRI demonstrating bilateral peritoneal pseudocysts (black arrows) in a pre-menopausal female. The normal left ovary is shown on the image (white arrow) and a normal right ovary was identified lying adjacent to the right sided pseudocyst on an other image. References: N. Bharwani; London, UNITED KINGDOM Page 15 of 48

16 Fig. 6: Figure 5. Coronal T2-weighted MRI demonstrating bilateral peritoneal pseudocysts (black arrows) in a pre-menopausal female. The normal left ovary is shown on the image (white arrow) and a normal right ovary was identified lying adjacent to the right sided pseudocyst on an other image. References: N. Bharwani; London, UNITED KINGDOM PPCs typically appear irregular in shape and reflect the invaginations of surrounding structures because they do not have a true wall themselves (walls are formed by surrounding organs and adhesions)( Figure 7, Figure 8, Figure 9 and Figure 10) (3). Peritoneal adhesions extend to the surface of the ovary and may distort the ovarian contour but do not penetrate the ovarian parenchyma. As fluid accumulates and becomes trapped by these adhesions, complex cystic masses form surrounding the ovary such that the ovaries appear entrapped within the cystic lesion (9). This appearance has been described as a 'spider's web' or 'entrapped ovary' appearance where a morphologically normal ipsilateral ovary is identified within the 'web' of adhesions (Figure 11). The position of the ovary is variable and it can be centrally or eccentrically placed. It is important not to confuse the ovary for a solid tumour nodule lying in the midst of a complex adnexal mass. Page 16 of 48

17 Fig. 7: Figure 7. Gray scale ultrasound demonstrating a septated anechoic irregular fluid collection in the left adnexa that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst (black arrows). The left ovary is identified adjacent to the left pelvic side wall (white arrow). References: N. Bharwani; London, UNITED KINGDOM Fig. 8: Figure 8. Gray scale ultrasound demonstrating a large septated anechoic fluid collection in the right adnexa that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst (black arrows). The right ovary is identified at the periphery of the pseudocyst (white arrow) and contains a follicular cyst. References: N. Bharwani; London, UNITED KINGDOM Page 17 of 48

18 Fig. 9: Figure 9. Gray scale ultrasound demonstrating a large anechoic fluid collection in the pelvis that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst. Both ovaries were identified on the periphery of the pseudocyst (not shown). References: N. Bharwani; London, UNITED KINGDOM Page 18 of 48

19 Fig. 10: Figure 10. Post-constrast axial CT through the pelvis demonstrates extensive fluid in both adnexal regions that conforms to the contours of adjacent structures (black arrows) in keeping with a peritoneal pseudocyst. Thin enhancing septae are seen to traverse the fluid (black arrowheads). * = Uterus. References: N. Bharwani; London, UNITED KINGDOM Page 19 of 48

20 Fig. 11: Figure 11. Gray scale ultrasound image demonstrating a typical 'spider web' pattern with loculated fluid and adhesions related to a normal appearing ovary. The ovary can be positioned centrally within the 'web' or lie in an eccentric position as in this example (white arrow). A low resistence trace was obtained from vessels in the septae in keeping with vessels running in the bridging mesothelial tissue. References: N. Bharwani; London, UNITED KINGDOM In the presence of the typical imaging features described above the diagnosis of PPC is relatively straightforward, particularly when accompanied by an appropriate clinical history. However, diagnosis is often more complex and PPCs can easily be misdiagnosed. Common pitfalls are outlined below: PPC simulating tubal disease: PPC can sometimes simulate a hydrosalpinx with entrapped fluid forming an oblong loculation adjacent to the uterus (Figure12 and Figure13). Nodular mesothelial tissue can project within the lumen, creating the classic 'cogwheel' appearance associated with a dilated fallopian tube. The adhesions extending partially within the fluid collection can also Page 20 of 48

21 be mistaken for the folded/convoluted appearance of the tube. Occasionally, peritoneal inclusion cysts can contain echogenic material and take on a tubular configuration, simulating the appearance of pyosalpinx; however, the patients are not symptomatic and do not have a fever or raised inflammatory markers. The distinction between tubal pathology and peritoneal inclusion cyst relies on images discriminating normal ovary housed within a peritoneal inclusion cyst from one being impinged upon and even distorted by an adjacent tubal structure (9). Fig. 12: Figure 12. Gray scale ultrasound image demonstrating a tubular peritoneal pseudocyst in the right adnexa lying adjacent to a normal right ovary (white arrow). Appearances mimic those of a hydrosalpinx. References: N. Bharwani; London, UNITED KINGDOM Page 21 of 48

22 Fig. 13: Figure 13. Gray scale ultrasound image demonstrating a tubular peritoneal pseudocyst in the left adnexa lying adjacent to a normal left ovary (white arrow). Appearances mimic those of a hydrosalpinx. References: N. Bharwani; London, UNITED KINGDOM PPC simulating a para-ovarian cyst: When the peritoneal adhesions are not extensive, small fluid collections contiguous with the adnexa may be mistaken for para-ovarian cysts (Figure14). True or primary paraovarian cysts are not caused by adhesions and appear as single or multiple, typically unilocular, thin walled cystic masses separate from the ovary in the broad ligament. Identification of a normal ipsilateral ovary separate from the cyst is helpful in diagnosing a para-ovarian cyst (17). Page 22 of 48

23 Fig. 14: Figure 14. Gray scale ultrasound images demonstrating an ovoid peritoneal pseudocyst in the right adnexa (black arrow) lying adjacent to the uterus. A normal right ovary is identified separate to the lesion (white arrow). Appearances mimic those of a para-ovarian cyst. References: N. Bharwani; London, UNITED KINGDOM PPC simulating an ovarian malignancy: Extensive adhesions can form irregular and thick septations and a complex cystic mass which is difficult to differentiate from a malignant ovarian neoplasm (Figure15 and Figure16). Low level internal echoes can also add to the confusion. The key to differentiation on imaging is the identification of a normal ipsilateral ovary. Fig. 15: Figure 15. Gray scale ultrasound image demonstrating a complex peritoneal pseudocyst in the right adnexa with thickened nodular septations (white arrowheads) mimicking the appearance of an ovarian malignancy. The right ovary is identified on the periphery (white arrow). References: N. Bharwani; London, UNITED KINGDOM Page 23 of 48

24 Fig. 16: Figure 16. The complex left adnexal mass with enhancing thickened septations (black arrows) demonstrated on this post-contrast coronal T1-weighted fat suppressed MR image could easily be mistaken for a primary ovarian malignancy however a morphologically normal left ovary was identified separately on an adjacent section. References: N. Bharwani; London, UNITED KINGDOM Differential Diagnosis *Para-ovarian cyst. *Dilated fallopian tube (hydro-, haemato- or pyo-salpinx). *Ovarian neoplasm - benign, borderline or malignant. Loculated ascites. Lymphangioma. Page 24 of 48

25 Mesenteric or Omental cysts. Pseudomyxoma peritonei. * 'Top' differential diagnoses which cause the greatest diagnostic challenge. Natural History PPCs have an indolent course in the majority of patients, growing slowly as fluid is secreted from the ovaries and not reabsorbed by the peritoneum. In those that are treated, 30-50% have recurrent collections (8;18) and malignant transformation has previously been reported (19) although the risk appears low. In our patient cohort of 11 patients, none of the patients had hormonal manipulation or surgical intervention. 8 of 11 patients have been followed up long term with imaging (up to 3 years). The natural history of the peritoneal pseudocysts in these patients was variable. In some patients the pseudocysts remained stable in size, while others demonstrated a slow increase in size until they became symptomatic requiring treatment and others demonstrated a spontaneous reduction in size. Four patients underwent US-guided drainage procedures (some repeatedly) and experienced symptomatic relief following drainage. Unfortunately all of the pseudocysts recurred following treatment with an interval between 6 days and 1 year before further drainage was required. The clinical course in one of these patients is illustrated in Figure 17. Fig. 17: Figure year old female with previous proctocolectomy and pouch formation. (a) Initial ultrasound performed during acute presentation with pelvic Page 25 of 48

26 discomfort and abdominal distention shows a large pelvic fluid collection with a normal right ovary identified on the periphery. The fluid collection conforms to the contour of the pelvic viscera in keeping with a peritoneal pseudocyst (PPC). (b) Following ultrasound-guided drainage, there is no significant fluid identified in the pelvis. The normal right ovary is identified again. (c) 2 months following drainage the patient reattended for follow-up imaging which showed re-accumulation of fluid around a normal right ovary. The patient was asymptomatic at this point. (d) The patient re-presented for routine follow-up one year after the initial drainage and the peritoneal pseudocyst was noted to have recurred (the ovary was identified separately to the collection). As the patient remained asymptomatic, there was no further intervention. (e) 2months later the patient underwent further ultrasound which showed a spontaneous reduction in the size of the PPC. (f) Further imaging at an interval of one year showed the PPC starting to re-accumulate. White arrow = Right Ovary. References: N. Bharwani; London, UNITED KINGDOM Management Options and Follow-up Conservative: Observation with serial imaging in asymptomatic patients with more aggressive treatment if symptoms develop. Oral contraceptive pill to suppress ovulation and therefore decrease the formation of ovarian fluid. Minimally-invasive / Radiological: Image-guided drainage. Symptomatic PPCS are generally accessible to US-guided drainage or aspiration via a trans-abdominal route. If access is difficult the pseudocyst may be amenable to trans-vaginal or CT-guided treatment. Surgical: Laparoscopic or open surgical resection of adhesions is only necessary in selected cases. Surgery is associated with a recurrence rate of 30-50% (8). Images for this section: Page 26 of 48

27 Fig. 1: Figure 1. (a) Gray scale ultrasound, (b) axial T2-weighted MRI and (c) axial fat saturated post-contrast T1-weighted MRI through a left adnexal peritoneal pseudocyst (black arrows). The PPC appears anechoic on ultrasound however the contents return high signal intensity on the T1-weighted fat saturdated images in keeping with haemorrhage. The morphologically normal left ovary is seen on the periphery (which arrows). The patient has had a previous right iliac fossa renal transplant (*). Page 27 of 48

28 Fig. 2: Figure 2. Gray scale ultrasound image demonstrating a septated fluid collection that conforms to the contours of the peritoneal cavity with a normal appearing right ovary identified eccentrically (white arrow). Fig. 3: Figure 3. Gray scale ultrasound image demonstrating a small triangular septated fluid collection (black arrow) that does not have a true cyst wall in the left adnexal region. A normal appearing left ovary is identified adjacent to the fluid (white arrow) and is noted to contain a single follicle (black arrowhead). Page 28 of 48

29 Fig. 4: Figure 4. Gray scale ultrasound image demonstrating an irregular septated fluid collection in the left adnexa that conforms to the surrounding structures. A normal appearing left ovary is identified adjacent to the fluid (white arrow). Page 29 of 48

30 Fig. 5: Figure 5. Coronal T2-weighted MRI demonstrating bilateral peritoneal pseudocysts (black arrows) in a pre-menopausal female. The normal left ovary is shown on the image (white arrow) and a normal right ovary was identified lying adjacent to the right sided pseudocyst on an other image. Page 30 of 48

31 Fig. 13: Figure 13. Gray scale ultrasound image demonstrating a tubular peritoneal pseudocyst in the left adnexa lying adjacent to a normal left ovary (white arrow). Appearances mimic those of a hydrosalpinx. Fig. 14: Figure 14. Gray scale ultrasound images demonstrating an ovoid peritoneal pseudocyst in the right adnexa (black arrow) lying adjacent to the uterus. A normal right ovary is identified separate to the lesion (white arrow). Appearances mimic those of a para-ovarian cyst. Page 31 of 48

32 Fig. 15: Figure 15. Gray scale ultrasound image demonstrating a complex peritoneal pseudocyst in the right adnexa with thickened nodular septations (white arrowheads) mimicking the appearance of an ovarian malignancy. The right ovary is identified on the periphery (white arrow). Page 32 of 48

33 Fig. 16: Figure 16. The complex left adnexal mass with enhancing thickened septations (black arrows) demonstrated on this post-contrast coronal T1-weighted fat suppressed MR image could easily be mistaken for a primary ovarian malignancy however a morphologically normal left ovary was identified separately on an adjacent section. Page 33 of 48

34 Fig. 12: Figure 12. Gray scale ultrasound image demonstrating a tubular peritoneal pseudocyst in the right adnexa lying adjacent to a normal right ovary (white arrow). Appearances mimic those of a hydrosalpinx. Page 34 of 48

35 Fig. 11: Figure 11. Gray scale ultrasound image demonstrating a typical 'spider web' pattern with loculated fluid and adhesions related to a normal appearing ovary. The ovary can be positioned centrally within the 'web' or lie in an eccentric position as in this example (white arrow). A low resistence trace was obtained from vessels in the septae in keeping with vessels running in the bridging mesothelial tissue. Page 35 of 48

36 Fig. 10: Figure 10. Post-constrast axial CT through the pelvis demonstrates extensive fluid in both adnexal regions that conforms to the contours of adjacent structures (black arrows) in keeping with a peritoneal pseudocyst. Thin enhancing septae are seen to traverse the fluid (black arrowheads). * = Uterus. Page 36 of 48

37 Fig. 9: Figure 9. Gray scale ultrasound demonstrating a large anechoic fluid collection in the pelvis that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst. Both ovaries were identified on the periphery of the pseudocyst (not shown). Page 37 of 48

38 Fig. 8: Figure 8. Gray scale ultrasound demonstrating a large septated anechoic fluid collection in the right adnexa that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst (black arrows). The right ovary is identified at the periphery of the pseudocyst (white arrow) and contains a follicular cyst. Fig. 7: Figure 7. Gray scale ultrasound demonstrating a septated anechoic irregular fluid collection in the left adnexa that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst (black arrows). The left ovary is identified adjacent to the left pelvic side wall (white arrow). Page 38 of 48

39 Fig. 6: Figure 5. Coronal T2-weighted MRI demonstrating bilateral peritoneal pseudocysts (black arrows) in a pre-menopausal female. The normal left ovary is shown on the image (white arrow) and a normal right ovary was identified lying adjacent to the right sided pseudocyst on an other image. Page 39 of 48

40 Fig. 17: Figure year old female with previous proctocolectomy and pouch formation. (a) Initial ultrasound performed during acute presentation with pelvic discomfort and abdominal distention shows a large pelvic fluid collection with a normal right ovary identified on the periphery. The fluid collection conforms to the contour of the pelvic viscera in keeping with a peritoneal pseudocyst (PPC). (b) Following ultrasoundguided drainage, there is no significant fluid identified in the pelvis. The normal right ovary is identified again. (c) 2 months following drainage the patient re-attended for followup imaging which showed re-accumulation of fluid around a normal right ovary. The patient was asymptomatic at this point. (d) The patient re-presented for routine followup one year after the initial drainage and the peritoneal pseudocyst was noted to have recurred (the ovary was identified separately to the collection). As the patient remained asymptomatic, there was no further intervention. (e) 2months later the patient underwent further ultrasound which showed a spontaneous reduction in the size of the PPC. (f) Further imaging at an interval of one year showed the PPC starting to re-accumulate. White arrow = Right Ovary. Page 40 of 48

41 Conclusion Peritoneal pseudocysts can present a diagnostic dilemma in the pre-menopausal female and knowledge of the clinical context and typical imaging features can avoid unnecessary surgery. Imaging plays an important role in the follow-up and minimally invasive treatment of these benign lesions. Image Interpretation Pearls: Typical clinical history with previous surgery or intra-peritoneal inflammation Cyst conforms to the adjacent pelvic structures and adhesions resulting in an irregular contour Deformable shape Internal septations resulting in 'spider's web' or 'entrapped ovary' appearance Normal ipsilateral ovary visible centrally or eccentrically May contain internal echoes May fluctuate in size Amenable to image-guided drainage for symptomatic relief Images for this section: Page 41 of 48

42 Fig. 9: Figure 9. Gray scale ultrasound demonstrating a large anechoic fluid collection in the pelvis that conforms to the contours of the pelvic viscera and pelvic adhesions in keeping with a peritoneal pseudocyst. Both ovaries were identified on the periphery of the pseudocyst (not shown). Page 42 of 48

43 Fig. 3: Figure 3. Gray scale ultrasound image demonstrating a small triangular septated fluid collection (black arrow) that does not have a true cyst wall in the left adnexal region. A normal appearing left ovary is identified adjacent to the fluid (white arrow) and is noted to contain a single follicle (black arrowhead). Page 43 of 48

44 Fig. 4: Figure 4. Gray scale ultrasound image demonstrating an irregular septated fluid collection in the left adnexa that conforms to the surrounding structures. A normal appearing left ovary is identified adjacent to the fluid (white arrow). Page 44 of 48

45 Fig. 5: Figure 5. Coronal T2-weighted MRI demonstrating bilateral peritoneal pseudocysts (black arrows) in a pre-menopausal female. The normal left ovary is shown on the image (white arrow) and a normal right ovary was identified lying adjacent to the right sided pseudocyst on an other image. Page 45 of 48

46 Fig. 11: Figure 11. Gray scale ultrasound image demonstrating a typical 'spider web' pattern with loculated fluid and adhesions related to a normal appearing ovary. The ovary can be positioned centrally within the 'web' or lie in an eccentric position as in this example (white arrow). A low resistence trace was obtained from vessels in the septae in keeping with vessels running in the bridging mesothelial tissue. Page 46 of 48

47 Personal Information Dr Nishat Bharwani, Dr Mary E Crofton. Department of Radiology, St Mary's Hospital, Imperial College Healthcare NHS Trust, Praed Street, London W2 1NY, United Kingdom. References (1) Vallerie AM, Lerner JP, Wright JD, Baxi LV. Peritoneal inclusion cysts: a review. Obstet Gynecol Surv 2009; 64(5): (2) Sohaey R, Gardner TL, Woodward PJ, Peterson CM. Sonographic diagnosis of peritoneal inclusion cysts. J Ultrasound Med 1995; 14(12): (3) Kurachi H, Murakami T, Nakamura H, Hori S, Miyake A, Kozuka T et al. Imaging of peritoneal pseudocysts: value of MR imaging compared with sonography and CT. AJR Am J Roentgenol 1993; 161(3): (4) Hoffer FA, Kozakewich H, Colodny A, Goldstein DP. Peritoneal inclusion cysts: ovarian fluid in peritoneal adhesions. Radiology 1988; 169(1): (5) Hederstrom E, Forsberg L. Entrapped ovarian cyst. An unusual case of persistent abdominal pain. Acta Radiol 1990; 31(3): (6) Lees RF, Feldman PS, Brenbridge AN, Anderson WA, Buschi AJ. Inflammatory cysts of the pelvic peritoneum. AJR Am J Roentgenol 1978; 131(4): (7) Weiss SW, Tavassoli FA. Multicystic mesothelioma. An analysis of pathologic findings and biologic behavior in 37 cases. Am J Surg Pathol 1988; 12(10): (8) Ross MJ, Welch WR, Scully RE. Multilocular peritoneal inclusion cysts (so-called cystic mesotheliomas). Cancer 1989; 64(6): (9) Kim JS, Lee HJ, Woo SK, Lee TS. Peritoneal inclusion cysts and their relationship to the ovaries: evaluation with sonography. Radiology 1997; 204(2): Page 47 of 48

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