One-hundred and ten lesions were Bosniak category I, II (benign) with thin wall, no/or thin septations, no calcifications, density 0-20HU, no enhancement after intravenous administration. [Fig 2-6]

Fig. 5: 5. Bosniak I category : Coronal (A) and transverse (C) contrast-enhanced CT scans show a single, large cyst, in the right kidney with thin walls, no septa, or calcification which contains fluid with attenuation of water (2,6HU).

Fig. 6: 6. Bosniak II category: Transverse (A) unenhanced, (B) contrast-enhanced, Coronal (C) and , Sagittal (D) CT scans show a large cyst in the upper pole of right kidney that contains fluid with attenuation of water (9,6HU), with thin walls and hairline-thin calcified septa(yellow arrow). There is no measurable enhancement within the mass. There is another simple cyst (Bosniak I) in the lower pole of the same kidney.

Ten lesions were Bosniak category IIF with calcium, or high density. After 2 years follow up no changes were observed. [Fig. 7-8]

Fig. 7: 7. Bosniak IIF category: Hyperdense benign cyst; category IIF lesion Transverse (A) unenhanced and (B) contrast-enhanced CT scans show a small, dense (29,6HU) mass protruding from the outermargin of the right kidney. The lesion is homogeneous and smoothly marginated and did not enhance following intravenous administration of contrast material (31HU after IV contrast media). A follow-up scan obtained 6months and a year later showed no change.

Fig. 8: 8. Bosniak IIF category: Hyperdense benign cyst; category IIF lesion. Transverse (A) unenhanced and (B) contrast-enhanced CT scans show a small hyperdense (60HU), with specific margins lesion in the parenchyma of the left kidney that lightly enhanced (less than 10HU). A follow up scan after 6, 12 and 24 months showed no important changes in size and density.

In one case [Fig. 9] of an 82-years-old man, with chronic renal failure because of kidney and ureter stones and hydronephrosis, there was a severe skepticism if the lesion should be placed in category IIF (complicated cyst) and have close follow-up or in category III and have nephrectomy (cystic carcinoma). The lesion had heterogeneity without significant enhancement and no any obvious septations. Because of the age of the patient and the medical history at first he was treated conservatively. At a follow up CT scan there were not any changes in the appearance but  then a MRI scan was performed which showed  a thickened wall and multiple thickened and slightly nodular septa within the mass. The patient underwent nephrectomy and a benign complex chronic hemorrhagic renal cyst was diagnosed.

Fig. 9: 9. Bosniak III category: Transverse (A) unenhanced and (B) contrast-enhanced CT scans in an 82-years-old man, with chronic renal failure because of kidney and ureter stones and hydronephrosis, show an exophytic mass in the lower pole of the left kidney (C) with heterogeneity (yellow arrow), grossly thickened and irregular wall with no obvious septaes. There was a severe skepticism if the lesion was a complicated (hemorrhagic) cyst (Bosniak IIF) or a suspicious renal cystic mass (Bosniak III) and therefore had a nephrectomy. Because of the age of the patient and the medical history at first he was treated conservatively. 6-months later he had a follow up CT with no changes of the findings but a MRI scan; Coronal T2-weighted MR image (D) showed a thickened wall and multiple thickened and slightly nodular septae within the mass. The patient underwent nephrectomy and a benign complex chronic hemorrhagic renal cyst was diagnosed.

Four lesions [Fig. 9, 10, 11B) were Bosniak category III with enhanced wall, thick septations or coarse calcifications, all were surgically resected (nephrectomy) and then evaluated histologically. Three of them were malignant and one was a hemorrhagic cyst [Fig.9]. In one patient [Fig. 11,12] there were two cystic lesions in the same kidney that proved to be two independent cystic cell carcinomas. The first one, in the upper pole [Fig.11B], was a multicystic lesion with multiple septa of varying thickness involving the upper pole of the left kidney. The lesion was considered to be Bosniak III. The second one, in the lower pole of the same kidney, was a single cyst with a thick mural calcification (Fig.11, 12 B, C, D, E), and a highly enhanced nodule (34->92HU) adjacent to the wall. This lesion was placed in Bosniak IV category. 

Fig. 11: Fig. 11-12 (same patient): Bosniak III-IV categories cystic lesions in a 41-years old woman with no medical history. Coronal contrast-enhanced CT scan (A) shows two cystic lesions in the upper and lower pole of the left kidney. Transverse (B) unenhanced and contrast-enhanced CT scans at the upper pole level show a multicystic lesion with multiple septa of varying thickness. The lesion is considered to be Bosniak III category. Transverse (C) unenhanced and contrast-enhanced CT scans at the lower pole level show a single cystic lesion with thick mural calcification (Fig.11,A,C 12.D, E), and a highly enhanced nodule (34->92HU) adjacent to the wall. The lesion placed in Bosniak IV category. The patient underwent nephrectomy and a low grade clear cell carcinoma was diagnosed in both lesions on histological evaluation.

Fig. 12: Fig. 11-12: Fig. 11-12 (same patient): Bosniak III-IV categories cystic lesions in a 41-years old woman with no medical history. Coronal contrast-enhanced CT scan (A) shows two cystic lesions in the upper and lower pole of the left kidney. Transverse (B) unenhanced and contrast-enhanced CT scans at the upper pole level show a multicystic lesion with multiple septa of varying thickness. The lesion is considered to be Bosniak III category. Transverse (C) unenhanced and contrast-enhanced CT scans at the lower pole level show a single cystic lesion with thick mural calcification (Fig.11,A,C 12.D, E), and a highly enhanced nodule (34->92HU) adjacent to the wall. The lesion placed in Bosniak IV category. The patient underwent nephrectomy and a low grade clear cell carcinoma was diagnosed in both lesions on histological evaluation.

Four lesions [Fig. 11-18] were Bosniak category IV with enhanced, thick wall and septations, small nodules and calcification. All of them were malignant. In two cases, in the sonographic images [Fig. 13A, 14A.] there was a “solid” appearance of whole or part of the lesion that came in comparison with the CT findings. Pathology evaluation explained that bloody debris in the lesions created that “solid” appearance on the sonogram.

Fig. 13: 13. Bosniak IV category: Cystic renal neoplasm in a 61-years old man with no medical history Sonogram (A) reveals a large mass at the lower pole of the right kidney with septations and heterogeneity in different parts (considered to be hemorrhagic substances). Transverse (B, D) contrast-enhanced CT scans show a cystic mass in the lower pole of the right kidney, with septations (yellow arrow) and a focal thickened (9mm) enhanced (55HU after IV contrast media)wall (C,D). No enhancement of the central portion of the mass was noted (the fluid in the central portion of the mass measures 15HU)

Fig. 14: 14. Bosniak IV category cystic lesion in an 80-years old man with benign prostatic hyperplasia A. Sonogram reveals a large mass at the lower pole of the right kidney. The mass contains multiple echoes with no through transmission, suggesting a solid tumor. B. Coronal (B) contrast-enhanced CT scan: A section taken through the lesion reveals a round, smooth cystic lesion with a solid enhancing nodule adjacent to the wall.

Fig. 16: 16. Same patient as Fig. 14. Transverse (A,C) unenhanced and (B,D) contrast-enhanced CT scans at different levels of the cystic lesion show no enhancementof the lesion, except in the nodules at the periphery which had significant enhancement (40HU : 44,9->79,2HU and 36->78,9HU). A right nephrectomy was performed and a cystic papillary RCC filled with bloody debris was found. Viable nodules was found in the wall of the lesion. The nature of the debris apparently created the “solid” appearance on the sonogram.

Fig. 17: 17. Bosniak IV category cystic lesion in a 60- years old woman with atypical abdominal pain Transverse (A,C) unenhanced and (B,D) contrast-enhanced CT scans show a lesion in the upper pole of the left kidneywith high density (C)(23,4HU), mild enhancement of the central portion of the mass (D) (~10HU) and thick calcification insite the lesion. The lesion considered to be more solid rather than cystic and placed in Bosniak IV category.

Fig. 18: 18. Same patient as Fig. 17. Moreover enhanced nodularity along the greater omentum and parietal mesenterium observed (A,B) (yellow arrow) (peritoneal carcinomatosis) (A,B). A metastatic papillary renal cell carcinoma was diagnosed on histological evaluation.