Answer
Ultrasonography often demonstrates single or multiple renal masses that have low-level echoes (see the the first image below). Occasionally, the ultrasonographic findings may appear normal because of the small size of the renal nodules (see the second image below). In addition, varying degrees of hydronephrosis may be seen because of compression of the renal hilum that is caused by lymph nodes or obstruction of the ureters. [20, 4]


On sonograms, a perirenal hypoechoic halo is characteristic of perirenal lymphoma (see the image below).

The degree of confidence with the ultrasonographic assessment of renal involvement is lower than that of CT scanning or MRI; however, in patients with perirenal involvement, the pattern of a halo sign is a characteristic finding.
As a result of the homogeneous nature of large lesions, these lesions appear hypoechoic on ultrasonography, but without enhanced through-transmission. Occasionally, differentiating large lesions from a simple or a complicated cyst is difficult. If the lesions are small or if the nature of involvement is diffuse, the ultrasonographic findings can be normal.
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Contrast-enhanced computed tomography (CT) scan obtained during the pyelographic phase for staging in a 17-year-old male adolescent with known lymphoma. This image reveals a hypoattenuating nodular pattern of different-sized lesions in both kidneys that represent bilateral renal lymphoma. Hypoattenuating nodes are also shown in the retroperitoneum.
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Computed tomography scan in a 17-year-old male adolescent with known lymphoma (same patient as in the previous image). This image was obtained 7 months after the initiation of chemotherapy in the patient and reveals complete resolution of the bilateral hypoattenuating lesions. The appearance and function of the kidneys are normal. Note the complete resolution of the retroperitoneal nodes.
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Contrast-enhanced computed tomography scan in a 15-year-old male adolescent with non-Hodgkin lymphoma. This image shows a bilateral pattern of multiple small nodules that are almost of equal size and involve both kidneys.
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Sagittal baseline sonogram in a 15-year-old male adolescent with non-Hodgkin lymphoma. This image shows near-normal architecture of the left kidney. Both kidneys were reported as normal (left kidney size, 11.4 X 5.7 cm), and no indication of hydronephrosis was noted.
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Contrast-enhanced computed tomography scan obtained during the nephrographic phase in a 93-year-old woman with non-Hodgkin lymphoma, in whom renal lymphoma mimicked renal cell carcinoma. This image reveals a single mass with heterogeneous attenuation that involves the right kidney, as well as an associated lymphadenopathy in the right side of the retroperitoneum. The findings suggest renal cell carcinoma with ipsilateral adenopathy. A normal variant of an extrarenal pelvis is noted in the left side.
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Contrast-enhanced, breath-hold, T1-weighted magnetic resonance image (MRI) (repetition time, 190 ms; echo time, 4 ms) in a 93-year-old woman with non-Hodgkin lymphoma. This image shows a mass with heterogeneous signal intensity in the right kidney; areas of low signal intensity reveal necrosis in the mass. MRI was performed to assess the renal vascular pedicle and inferior vena cava, both of which were free of tumor. Because of the patient's history of non-Hodgkin lymphoma (for which she received treatment), biopsy was performed to exclude renal cell carcinoma. The diagnosis of renal lymphoma was proven, and the patient received appropriate treatment.
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Intravenous urogram obtained during the excretory phase in a 52-year-old woman with non-Hodgkin lymphoma who presented with flank pain. This image reveals a near-normal renal collecting system, with slightly enlarged kidneys and minimal narrowing of the proximal ureter that are suggestive of an external mass effect.
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Computed tomography (CT) scan in a 52-year-old woman with non-Hodgkin lymphoma. This image reveals diffuse renal lymphoma, in which diffuse, small nodules are scattered throughout both kidneys. The finding was not appreciated on the intravenous urogram and was only seen on contrast-enhanced CT scans. In fact, nonenhanced CT findings (not shown) were almost normal. The slight, narrowed ureter at the proximal portion, as seen on the urogram, was attributed to nephromegaly and compression of the ureter by the medial aspect of the kidney.
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Autopsy specimen from a 52-year-old woman with non-Hodgkin lymphoma. Numerous lymphomatous nodules are visible throughout the kidneys.
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Computed tomography scan in a 36-year-old woman. This image reveals multiple lymphomatous masses that involve the right kidney, in which the largest mass shows areas of necrosis. A few lymph nodes are evident in the right-sided renal pedicle. Note that the patient has splenomegaly, with probable involvement of the liver and associated ascites and a vertebral bony lesion.
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Computed tomography scan in a 53-year-old woman with lymphoma. A large relatively homogeneous mass involving the left kidney is associated with ipsilateral adenopathy. Note the beginning of minimal necrotic changes in the renal mass and the para-aortic nodes (cursors). A lymphomatous mass is seen in the liver. The pattern can be easily mistaken for renal cell carcinoma and associated with retroperitoneal adenopathy and hepatic metastasis. Note the thick-walled loop of small bowel from lymphoma anterior to the nodal mass.
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Contrast-enhanced computed tomography (CT) scan in a 28-year-old woman with non-Hodgkin lymphoma, who presented with left flank pain. A renal sonogram (not shown) depicted left hydronephrosis and renal mass. This CT scan shows retroperitoneal extension of lymphoma to the left kidney, in which a large mass in the left side of the retroperitoneum extends into the left kidney. Adenopathy in the left hilar region appears to displace the renal vein and surround the renal artery without obstructing the blood flow. The posterior collecting system is dilated as a result of obstruction of the ureter by adenopathy that is present more caudally in the retroperitoneum (not shown).
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Contrast-enhanced computed tomography scan in a 28-year-old woman with non-Hodgkin lymphoma (same patient as in the previous image) that was obtained to evaluate response to chemotherapy approximately 5 months after the patient underwent treatment. This image shows a mild degree of atrophy in the left kidney but complete resolution of the adenopathy and mass. The atrophy may also have been the result of long-standing hydronephrosis.
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Sonogram in a 62-year-old man who presented with palpable flank masses demonstrates perirenal lymphoma without retroperitoneal adenopathy. Although the left kidney appears to show no indication of a mass or hydronephrosis, a hypoechoic but solid-appearing area surrounds the kidney. The ultrasonographic findings may simply represent a perirenal complicated fluid collection or edema; however, perirenal lymphoma should be considered. Because of the underlying renal disease, the echotexture is increased throughout the kidney. This study was followed by computed tomography scanning and magnetic resonance imaging.
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Nonenhanced computed tomography scan obtained in a 62-year-old man with a palpable flank mass and elevated levels of serum blood urea nitrogen and creatinine. This image shows large bilateral masses that cannot be distinguished from the renal parenchyma. A few calcifications are seen on the left side. No retroperitoneal adenopathy is noted.
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T2-weighted magnetic resonance image (repetition time, 2000 ms; echo time, 80 ms) in a 62-year-old man with a palpable flank mass. This image reveals homogeneous high signal intensity masses that surround the kidneys. The left kidney can be distinguished because of the collecting system and the vascular pedicle. Note the patency of the renal vascular pedicle in the left side.
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T2-weighted magnetic resonance image (repetition time, 2000 ms; echo time, 80 ms) in a 62-year-old man with a palpable flank mass. This image shows patency of the renal vascular pedicle on the right side. The normal renal parenchyma has a signal intensity that is slightly different from that of the surrounding perirenal mass. A diagnosis of perirenal lymphoma was proven by percutaneous biopsy.
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Computed tomography scan in a 72-year-old woman with a known diagnosis of non-Hodgkin lymphoma. This image shows perirenal lymphoma with retroperitoneal adenopathy. Massive retroperitoneal adenopathy, splenomegaly, and a bilateral rim of low-attenuating tissue that surrounds the kidneys are noted. These findings are typical of perirenal lymphoma. The spleen has a large area of low attenuation as a result of tumor infiltration. Adenopathy, splenomegaly, and the perirenal process completely resolved after chemotherapy.
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Nonenhanced computed tomography scan in a 22-year-old woman with non-Hodgkin lymphoma and elevated levels of blood urea nitrogen and creatinine. An infiltrative pattern of renal lymphoma is seen as lymphomatous infiltration within the interstitium of the kidneys, which causes bilateral nephromegaly. Note the areas of slightly lower attenuation and the preservation of the renal contour.
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Contrast-enhanced computed tomography scan in a 36-year-old woman. This image shows bilateral small masses of different sizes due to lymphoma with involvement of the kidneys. The right kidney is more involved than the left. Associated adenopathy is noted in the retroperitoneum.
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T1-weighted magnetic resonance image (repetition time, 650 ms; echo time, 25 ms) in a 36-year-old woman with bilateral renal lymphoma. This image reveals right-sided nephromegaly. No discrete nodule can be seen in the kidneys.
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T2-weighted magnetic resonance image (repetition time, 2200 ms; echo time, 90 ms) in a 36-year-old woman with bilateral renal lymphoma. This image reveals heterogeneous intensity of the kidneys. Detection of discrete nodules is difficult.
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Contrast-enhanced T1-weighted magnetic resonance image (repetition time, 650 ms; echo time, 25 ms) in a 36-year-old woman with bilateral renal lymphoma. This image reveals enlargement of the right kidney with diffuse low signal intensity. The discrete low-intensity lesion in the left kidney is better depicted on the contrast-enhanced image. Note the splenomegaly with splenic involvement and ascites.
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Axial sonogram in a 22-year-old woman with known lymphoma. A baseline sonogram was performed, which demonstrated renal lymphoma. This image depicts a large kidney with heterogeneous echotexture and poorly defined areas of hypoechogenicity. A mild degree of hydronephrosis is noted. After chemotherapy, follow-up ultrasonographic images showed complete resolution of the renal lymphoma.
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Gallium scan in a 55-year-old woman with known diffuse, poorly differentiated lymphoma who was admitted to the hospital because of renal failure. The patient had a creatinine level of 3. A sonogram (not shown) was performed and revealed no hydronephrosis. However, the echotexture of the kidneys was abnormal on the sonogram, and the possibility of renal lymphoma was suggested. This posterior view of the kidneys (Post) obtained at 72 hours after the injection of gallium-67 citrate shows multiple abnormal areas of increased uptake (arrows), particularly on the right side (R). This finding is consistent with renal involvement by lymphoma. Urinalysis results were normal, excluding underlying infection. Some residual gallium was noted in the colon. Gallium scan findings were normal 4 months after appropriate chemotherapy.