Imaging approach
4.5 Renal mass in patients with symptoms
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Figure 4.8 A nuclear bone scan done for research on bone aging showed a defect in the right kidney in this asymptomatic 75-year-old male. (a) Unenhanced CT reveals a very large low attenuation mass involving the right kidney. (b) Arterial phase CT shows exuberant peripheral enhancement. (c) Delayed image shows considerable enhancement but central low attenuation.
Nephrectomy was done after indeterminate biopsy and revealed a large oncocytoma Large lesions such as this commonly have central scar which is not clearly distinguishable from central necrosid thus there is overlap of imaging features between large RCC and large oncocytoma.
4.5 Renal mass in patients with symptoms
• A renal mass may be detected in a patient with signs or symptoms which may be non-specific but possibly associated with a renal source.
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Figure 4.9 A solid mass lesion in the left kidney treated with ablative therapy. (a) Unenhanced image shows bulge from upper pole of left (attenuation 22 HU). (b) After contrast for better definition of mass, attenuation was increased to 79 HU. (c) Percutaneous biopsy was performed followed by ablation with cryotherapy. The pathology result of the biopsy was oncocytoma.
• Flank pain, back pain, renal colic with or without hematuria commonly is investigated with unenhanced CT.
◦ If an exophytic renal mass is seen, particularly if the attenuation is higher than water (>20 HU), a contrast enhanced study should be done (Fig. 4.7).
◦ Small non-contour deforming renal masses can be missed with unenhanced CT. Thus, persistent hematuria without an explanation such as urolithiasis, should also stimulate contrast enhanced examination.
4.5 RENAL MASS IN PATIENTS WITH SYMPTOMS 65
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Figure 4.10 Evaluation for breast cancer in the 54-year-old female included PET/CT. (a) A coronal PET and Fused image of the kidneys reveals a hypermetabolic bulging region in the upper pole of the right kidney (arrows). (b) Unenhanced CT shows a right sided mass (arrows) with attenuation 31 HU and left sided mass 10 HU. (c) Coronal reformatted enhanced CT image shows the mass (148 HU) bulging medially from the right kidney whose shape is otherwise preserved.
This is the typical exophytic growth pattern of RCC. Note the left sided Bosniak 1 simple cyst with no enhancement post contrast.
◦ Investigation of hematuria is covered else where in the book. RCC is a not uncommon cause of hematuria (Figs. 4.1 and 4.2).
◦ Urothelial tumors also can cause hematuria, although upper tract transitional carcinoma (TCC) is considerably less common than RCC.
TCC can usually be detected with pre- and post-contrast axial CT (Fig. 4.14).
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Figure 4.11 A 50-year-old female have lung secondaries from cancer of the colon. (a) Staging CT demonstrates metastases in liver, right adrenal and upper pole of left kidney. (b) A more caudal image shows right renal lesions typical of metastases to the kidney (small, multiple with endophytic growth pattern, no bulging of the renal contour). This patient was treated with chemotherapy.
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Figure 4.12 A 51-year-old male suffering from lung cancer. (a) Staging CT shows soft tissue fullness in upper pole of the left kidney. (b) Contrast enhanced CT shows a large mildly enhancing lesion in left kidney, not causing bulging of the renal contour. (c) Coronal reformatted image nicely demonstrates the ‘bean’ growth pattern of this mass, although the kidney is slightly expanded there is no alteration of contour. Since this was somewhat atypical of metastasis (single large renal mass without other abdominal metastases) a biopsy was done which revealed metastatatic bronchogenic carcinoma.
4.5 RENAL MASS IN PATIENTS WITH SYMPTOMS 67
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Figure 4.12 (Continued)
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Figure 4.13 A 56-year-old male presented with hematuria. (a) A CT of the abdomen reveals very extensive retroperitoneal lymphadenopathy extending directly into and expanding the left kidney. This is a typical growth pattern of renal lymphoma, with multifocal renal masses, perirenal disease, or diffuse enlargement also occurring. Percutaneous biopsy of the retroperitoneal mass was done revealing B cell lymphoma. (b) Follow-up after chemotherapy 4 months later shows marked improvement with the kidney returning to near normal.
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Figure 4.14 A 76-year-old male with long smoking history developed hematuria. (a) Unen- hanced CT image shows expansion of renal pelvis, measuring 28 HU thus of soft tissue attenuation, not hydronephrosis. (b) After contrast the region (arrows) measures 65 HU, thus is enhancing excluding blood clot. Even without opacification of collecting system, or reformatted images, this is diagnostic of renal pelvic TCC. High grade TCC confined to collecting system was confirmed at nephroureterectomy.
Most renal TCC occurs in the renal pelvis, but may produce a central infiltrative mass with endophytic (bean not ball) growth pattern which is more typical of TCC rather than RCC, although there can be overlap, and RCC can invade the pelvis (Fig. 4.15).
• A renal mass may be discovered in a patient with signs and symptoms of urinary tract infection
◦ A renal abscess produces a focal mass
Imaging appearance of an abscess whether on US, CT, or MRI can overlap with that of tumor with central necrosis. However, in the clinical setting, of infection correct diagnosis can be suggested with confirmation by percutaneous aspiration, culture and drainage (Fig. 4.16).
With proper treatment most pyelonephritis and abscess resolve with no residua, except for possible focal scar.
Chronic, indolent, or previously treated pyogenic infections including uncommon infections such as tuberculosis and echinococcus can result in a complex, often calcified mass (Fig. 4.17). In such cases, prior imaging studies may be useful, as the appearance can simulate a renal tumor.