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Overview of Retroperitoneal Anatomy, Masses and Disease Spread Imaging

Overview of Retroperitoneal Anatomy, Masses and Disease Spread Imaging. Saeed Elojeimy MD- Phd 1 Mariam Moshiri MD 1 Puneet Bhargava MD 2 Sheriff Osman MD 1 Charles A Rohrmann MD 1. 1 Department of Radiology, University of Washington Medical Center, Seattle WA

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Overview of Retroperitoneal Anatomy, Masses and Disease Spread Imaging

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  1. Overview of Retroperitoneal Anatomy, Masses and Disease Spread Imaging SaeedElojeimyMD-Phd 1 MariamMoshiri MD 1 PuneetBhargava MD2 Sheriff Osman MD 1 Charles A RohrmannMD 1 1 Department of Radiology, University of Washington Medical Center, Seattle WA 2 Department of Radiology, University of Washington & VA Puget Sound Health Care System, Seattle WA

  2. Pretest unknown 1: can you name the fascial layer marked with the arrow ?

  3. Pretest unknown 2 : what is the diagnosis ?

  4. Pretest unknown 3 : what is the diagnosis ? MRI out of phase MRI in phase

  5. Pretest unknown 4 : what is the diagnosis ?

  6. Goals and Objectives 1. Review anatomy of the retroperitoneum 2. Illustrate pathways for disease spread in the retroperitoneum 3. Present an algorithmic approach for the differential diagnosis of retroperitoneal masses 4. Review pathognomonic findings of syndromes with RP involvement

  7. Introduction to RP Anatomy Borders: bordered anteriorly by peritoneal fasciae and posteriorly by the posterior continuation of the transversalis fascia (marked by thick blue line). Transversalis fascia Contents:ascending and descending colon, duodenum, pancreas, aorta, IVC, kidneys, adrenal gland, proximal ureters, and retroperitoneal fat. Posterior renal fascia Anterior renal fascia Lateroconal fascia Peritoneal fasciae

  8. RP anatomy RP fasciae Lateroconalfascia (LCF) Posterior renal fascia (PRF) aka Zuckerkandl’s fascia Anterior renal fascia (ARF) aka Gerota’s fascia ARF LCF PRF

  9. RP anatomy Interfascial planes Lateroconal: between layers of lateroconal fascia Retrorenal: Between layers of posterior renal fascia Retromesenteric: between layers of anterior renal fascia Retromesenteric plane Lateroconal plane Retrorenal plane

  10. RP anatomy A B C Axial CT images (A-C) showing progressive thickening and fluid dilatation of the retrorenalfascial plane (yellow arrows) secondary to inflammation/ infection. Note fluid extension in image C into the lateroconalplane (blue arrows).

  11. RP anatomy RP spaces Anterior pararenal space Perirenal space Posterior para-renal space

  12. RP anatomy RP spaces Anterior pararenal space (green highlight) • Borders: between peritoneum and ARF • Contents: ascending and descending colon, duodenum, and pancreas (Think GI)

  13. RP anatomy RP spaces Perirenal space (purple highlight) • Borders: between ARF and PRF • Contents: kidneys, adrenal glands, proximal ureters, perirenal fat, lymphatic vessels, and blood vessels (Think GU)

  14. RP anatomy RP spaces Posterior para-renal space (blue highlight) • Borders: between PRF and transversalis fascia • Contents: predominantly fat

  15. RP anatomy B A C A and B: Perirenalfluid (yellow arrow) secondary to calyceal rupture in a patient with right ureteric stone (blue arrow). Note lack of hydronephrosis, consistent with relief of obstruction secondary to calyceal rupture. C: Perirenal stranding in a patient with pyelonephritis(orange arrows).

  16. Pathways for disease spread Direct extension Lymphatic spread

  17. Pathways for disease spread Direct extension Disease can spread within the RP by dissecting through the interfascial planes (see examples in the following slides). In addition, The strategic location of the RP makes it a pathway for disease spread among the surrounding compartments including the pelvis, peritoneum and mediastinum as illustrated in the diagram on the right. Mediastinum Peritoneum RPspaces Pelvis

  18. Direct extension B A C Axial CECT images (A-C) showing a case of sigmoid rupture with air dissecting from pelvis (yellow arrows) into the RP (blue arrows) .

  19. Direct extension A B * * * * Coronal CT in a patient with a psoas abscess showing extension of infection and inflammatory fluid into the posterior pararenal spaces and interfascial planes (blue arrows). Axial CT showing acute pancreatitis with fluid and gas bubbles in anterior pararenal space (*) dissecting through retrorenalinterfascial plane (blue arrow), and extending into posterior RP space (yellow arrow).

  20. Direct extension A B * * * * * C D * * * Axial CECT (A-D) illustrating a case of acute pancreatitis with fluid in anterior pararenal space (*) extending anteriorly into the peritoneum (yellow arrow) and inferiorly into the pelvis (blue arrow).

  21. Pathways for disease spread Lymphatic spread Mediastinal and pleural lymph nodes Within the RP, the perinephric bridging septae connect the kidneys to pararenallymphatics which are inter-connected among themselves. The aorto-caval lymph nodes act as a bridge between RP lymphatics and lymph nodes in the chest and pelvis as illustrated in diagram on the left. Perirenal and pararenal lymphatics Aorto-caval Lymph nodes Pelvic and inguinal lymph nodes

  22. Lymphatic spread A D B C Axial (A-C) and coronal (D) CT images showing a case of lymphangiomatosis extending through lymphatics of the RP (blue arrows) and involving lymphatics of the posterior mediastinum (yellow arrows) and pelvis (orange arrows). Tiny calcifications/ phleboliths are related to additional hemangioma component.

  23. Overview of RP masses Other Renal Adrenal Pancreatic General recommendations for approaching retroperitoneal masses: Determine organ of origin. Look for tissue composition : cystic vs predominantly fatty vs soft tissue. Look for other features: +/- calcifications, enhancement compared to organ of origin. History and other clinical info: recent surgery, trauma.

  24. Renal masses Cystic Solid Bosniak classification1 Is there macroscopic fat ? No Yes -Angiomyolipoma -Renal cell carcinoma (RCC)2 -Transitional cell carcinoma -Lymphoma -Metastasis 1.To learn more about Bosniak classification, click on following link :Bosniak renal cyst classification | Radiology Reference Article | Radiopaedia.org 2. Notethat RCC can rarely contain macroscopic fat.

  25. Renal masses B A C A. Coronal CT showing a simple bosniak type 1 renal cyst (yellow arrow) B. Coronal CT showing a Bosniak type 3 renal cyst (blue arrows) with thick coarse calcification within wall (blue arrowhead) C. Coronal CT showing bilateral renal cysts in a patient with adult polycystic kidney disease (orange arrows)

  26. Renal masses A B C A. Axial CT showing a heterogeneous exophytic soft tissue renal mass consistent with RCC (yellow arrows) B. Axial CT showing a homogeneous large renal soft tissue mass consistent with lymphoma (blue arrows). C. Axial CT showing a fat containing renal mass consistent with angiomyolipoma.

  27. Adrenal masses Solid Cystic Is there macroscopic fat ? -Adrenal cyst -Adrenal hematoma Yes No Is there microscopic fat ?* -Myelolipoma No Yes -Adenoma -Metastasis -Adrenocortical carcinoma -Pheochromocytoma -Lymphoma * To learn more about microscopic fat and its detection,refer to the following article :CT and MR Imaging of Extrahepatic Fatty Masses of the Abdomen and Pelvis: Techniques, Diagnosis, Differential Diagnosis, and Pitfalls1

  28. Adrenal masses B A C A. Axial CT showing a right adrenal mass in a patient following MVC that resolved on follow-up imaging (not shown) consistent with an adrenal hematoma (yellow arrows) B. Axial CT showing a low density left adrenal cystic structure consistent with an adrenal cyst (blue arrows) C. Coronal CT showing a fat containing adrenal mass consistent with myelolipoma (orange arrows).

  29. Adrenal masses B A C A. Axial MRI images showing a right adrenal mass with high signal on in phase sequence (top, black arrows) that loses signal on out of phase sequence (bottom, yellow arrows) consistent with adrenal adenoma B. Axial CT of a patient with lung cancer showing a left adrenal metastasis (blue arrows) C. Coronal CT showing a case of lymphoma involving the right adrenal gland (orange arrowheads) and right kidney (orange arrows).

  30. Pancreatic masses Solid Cystic Lesion enhancement more or less compared to normal pancreatic tissue ? -Pancreatic pseudocyst -Microcystic serous adenoma -Mucinous cystic neplasm -Solitary and papillary epithelial neoplasm (SPEN) -Intraductal papillary mucinous tumor (IPMN) -Other: Cystic mets, lymphoma More Less -Pancreatic adenocarcinoma -Metastasis -Pheochromocytoma -Islet cell tumors (insulinoma, gastrinoma) -Metastasis

  31. Pancreatic masses B A C A. Axial CT image showing tiny cysts in pancreatic head characteristic of microcystic serous adenoma (blue arrowheads). B. Axial CT image showing an islet cell tumor (yellow arrows), hyperenhancing compared to normal pancreatic tissue (yellow arrowheads). C. Axial CT image a pancreatic adenocarcinoma (orange arrows), hypoenhancing compared to normal pancreatic tissue (orange arrowheads).

  32. Pancreatic masses * Axial (right) and coronal (left) CT images showing dilated pancreatic (yellow arrows) and hepatic (black arrows) ducts (double duct sign) caused by a pancreatic pseudocyst (marked with a star). Note scatterered pancreatic calcifications (yellow arrowheads, right and left images) consistent with chronic pancreatitis.

  33. Primary RP masses Solid Cystic -Lymphocele -Seroma -Pseudocyst -Abscess -Hematoma -Urinoma -Lymphangioma Does mass contain fat? No Yes -Lipoma -Liposarcoma -Teratoma -Mesoderm origin: leiomyoma/ sarcoma, lymphoma, RP fibrosis (lymphoma mimic). -Germ Cell tumors -Neurogenic and nerve sheath tumors: neurofibroma, neuroblastoma. -Metastasis

  34. Primary RP masses A C B A. Axial CT image in a patient post MVC showing a perirenal hematoma (yellow arrows) with active extravasation (yellow arrowheads). B. Axial CT showing a post-surgical lymphocele (blue arrows). Note surgical clips (blue arrowheads). C. Coronal CT showing a leiomyosarcoma (orange arrows) with IVC invasion (orange arrowheads).

  35. Other RP masses B A C A. Axial CT images showing a case of RP fibrosis (yellow arrows), a mimic for RP lymphoma. Lymphoma tends to displace aorta (yellow arrowheads) anteriorly, a differentiating feature not seen with RP fibrosis. B. Axial CT showing a RP soft tissue mass with multiple cystic regions and calcifications (arrow-heads) consistent with a teratoma. C. Axial CT large predominantly fat containing RP mass (orange arrow-heads) consistent with liposarcoma.

  36. Pathognomonic Findings of Syndromes with RP Involvement Birt-Hogg- Dube ? Left renal cancer Pulmonary cysts Erdheim-Chester ? Peri-renal fibrosis Interlobular septal thickening

  37. RP syndromes TuberousSclerosis Hepatic AML Bilateral AML ? Cortical Tubers Lung cysts

  38. RP syndromes Lymphangiomatosis Splenic lesions ? Bony lytic lesions 38

  39. Summary and Review Slides

  40. Summary 1. We reviewed retroperitoneal anatomy including retroperitoneal spaces, fasciae and interfascial planes. 2. We illustrated examples of retroperitoneal spaces and planes connecting to each other, and with other spaces in chest abdomen and pelvis. 3. We provided an algorithmic approach for approaching retroperitoneal masses. 4. We reviewed pathognomonic findings of syndromes that involve the retroperitoneum.

  41. Retroperitoneum Anatomy: Rule of 3’s APS ARF/RMP PRS LCF/LCP PRF/RRP PPS * Note that RP interfascial planes represent pathologic dilatation of corresponding RP fasciae .

  42. Pathways for Disease Spread Direct Extension Lymphatic Spread Chest LNs Mediastinum Pararenal LNS Aorto-caval LNs Peritoneum RPSpaces Pelvic and inguinal LNs Pelvis

  43. Summarized Algorithm for Approaching RP masses Pancreatic Renal Adrenal Primary RP Soft tissue Cystic Soft tissue Cystic Soft tissue Cystic Soft tissue Cystic • Pseudocyst • Mucinous and serous cystic neplasms • SPEN • IPMN • Cystic metastasis • Lymphoma Simple cyst • Lymphocele • Seroma • Pseudocyst • Abscess • Hematoma • Urinoma • Lymphangioma • Cyst • Hematoma • Metastasis • Adrenocortical carcinoma • Pheo-chromocytoma • Lymphoma 1 1 3 4 • Mesoderm tumors • Germ cell tumors • Neurogenic tumors • Metastasis 2 1 • RCC • TCC • Lymphoma • Metastasis • Pheo-chromocytoma • Islet cell tumors • Metastasis • Adeno-carcinoma • Metastasis • Lipoma • Liposarcoma • Teratoma AML Myelolipoma Adenoma 1. Contains macroscopic fat 2. Contains microscopic fat 3. Hyperenhancing compared to pancreatic tissue 4. Hypoenhancing compared to pancreatic tissue

  44. Post-test unknown 1: can you name the fascial layer marked with the arrow ?

  45. Unknown 1 answer: posterior renal fascia

  46. Post-test unknown 2 : what is the diagnosis ?

  47. Unknown 2 answer: lymphangioma

  48. Post-test unknown 3 : what is the diagnosis ? MRI out of phase MRI in phase

  49. Unknown 3 answer: adrenal adenoma MRI out of phase MRI in phase

  50. Post-test unknown 4 : what is the diagnosis ?

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