Forced diuresis ¹⁸F-fluorodeoxyglucose positron emission tomography/contrast enhanced in detection of carcinoma of urinary bladder diverticulum

A 48-year-old male presented with painless hematuria and left hip pain since 2 months. Atypical cells were found on urine cytology. Noncontrast computerized tomography of abdomen and pelvis showed a bladder diverticulum arising from right lateral wall of the urinary bladder and a lytic expansile lesion in sacrum and right acetabulum. Fine-needle aspiration cytology from the right acetabular lesion showed high grade metastatic poorly differentiated carcinoma. For localization of primary tumor and extent of metastatic involvement, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/contrast enhanced computerized tomography (CECT) was done, which revealed metabolically active metastatic disease in retroperitoneal and pelvic lymph nodes, right adrenal gland, multiple skeletal sites, and bilateral lungs in maximum intensity projection images. Due to suspected bladder malignancy, forced diuresis pelvic PET/computerized tomography (CT) was planned. Patient was given furosemide at a dose of 1 mg/kg body weight. Patient was advised oral fluid intake (around 1.5–2 L) and to hold urine after voiding for 2–3 times to allow maximum bladder distension. Forced diuresis pelvic PET/CT images were acquired approximately 2 h after whole body PET/CT imaging. It showed FDG avid soft tissue lesion in the diverticulum arising from right lateral wall of the urinary bladder [Figure 1] which was suggested as the primary malignant site. In view of multiple metastatic lesions and strongly suggested primary site in forced diuretic pelvic PET/CT, patient was given three cycles of chemotherapy and local radiotherapy to pelvis. Post treatment, whole body and forced diuretic ¹⁸F-FDG PET/CT showed a significant response in metastatic and primary sites [Figure 2], and it retrospectively confirmed the bladder diverticular malignancy. Prediuretic PET images did not reveal the primary in bladder diverticulum in both baseline and follow-up.

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Figure 1 Maximum intensity projection images of ¹⁸F-fluorodeoxyglucose positron emission tomography/contrast enhanced computerized tomography (¹⁸F-FDG PET/ CECT): (a) Revealed active metastatic disease in retroperitoneal and pelvic lymph nodes, right adrenal gland, multiple skeletal sites, and bilateral lungs (arrows). Prediuretic PET image (b) did not reveal the primary site. Axial sections of CECT (c, arrow) showed irregular opacification with contrast and thickening of mucosa of bladder diverticulum and forced diuresis pelvic PET/computerized tomography images (d and e) showed FDG avid soft tissue lesion in the diverticulum arising from right lateral wall of urinary bladder (arrows) suggested as the primary malignant site

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Figure 2 Maximum intensity projection images of ¹⁸F-fluorodeoxyglucose positron emission tomography/computerized tomography (¹⁸F-FDG PET/CT) post three cycles of chemotherapy and local radiotherapy showed a significant response in metastatic sites. (a) Prediuretic PET image (b) did not reveal the primary site even after posttreatment. Axial sections of CT images of pelvis (c, arrow) showed a soft tissue lesion in bladder diverticulum. Axial sections of forced diuresis fused pelvic PET/CT images (d and e) showed response to treatment in the bladder diverticular lesion (arrows)

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Urinary bladder diverticular carcinomas are uncommon with a lesser incidence of 0.8–10%.[1] Multiple modalities such as cystoscopy, CECT, and magnetic resonance imaging (MRI) are used for its diagnosis and staging. Cystoscopy is the most reliable method, but evaluation of tumors with narrow orifices is challenging.[2] Ultrasonography is useful for diagnosing patients with bladder diverticulum tumors, but evaluation of tumors in the dome or neck of the bladder is difficult.[3] With CECT, nonopacification of diverticulum due to occlusion of diverticular orifice by tumor occurs limits the detection of the primary tumor in some cases.[4] High intrinsic tissue contrast between urine and the tumor in the diverticulum makes T1- and T2-weighted MRI suitable for detection of primary bladder diverticular tumor and its perivesical spread.[4] But the major limitation of CECT and MRI is that only enlarged lymph nodes are considered abnormal for locoregional involvement.[2] Not much literature is available regarding role of ¹⁸F-FDG PET/CT in the detection of bladder diverticulum malignancy. ¹⁸F-FDG PET is limited in the detection of bladder cancers due to normal physiological excretion of FDG into the bladder which obscures the bladder wall lesions.[5] Forced diuretic ¹⁸F-FDG PET/CT has an important role in detection and staging of bladder diverticular carcinoma. Forced diuresis washes out FDG from the bladder, provides good lesion to background contrast, and enables detection of bladder tumors.[67] ¹⁸F-FDG PET/CT has got high sensitivity and specificity for distant metastasis detection in bladder carcinomas[8] and especially forced diuretic FDG PET/CT is more sensitive than CT in detecting locoregional lymph node metastases.[6] In the present case, detection of urinary bladder diverticular carcinoma by combination of the whole body and forced diuretic ¹⁸F-FDG PET/CT imaging is an interesting diagnostic feature. It also played a significant role in the detection of locoregional lymph node and distant metastatic involvement and response evaluation of bladder diverticular carcinoma which impacted patient management and prognosis.