Invasion of the mandible in gingivobuccal complex cancers: Histopathological analysis of routes of tumour entry and correlation with preoperative assessment.

OBJECTIVES: To determine the most accurate imaging modality predicting mandibular invasion in gingivobuccal (GB) complex cancers. To determine patterns of invasion and routes of tumour entry into the mandible by detailed histopathologic analysis. MATERIAL AND METHODS: Prospective observational study of GB Complex cancers juxtaposed with the mandible clinically necessitating some form of mandibular resection. Orthopantomogram (OPG), Multi Detector Computed Tomography (MDCT), DENTA scan and Single Photon Emission Computed Tomography scan (SPECT) were performed after which the patient was subjected to surgery. Histopathological assessment was systematically performed with serial cuts of the mandibular segment. RESULTS: Of 70 patients, MDCT was the most accurate with area under curve (AUC) of 0.833. OPG, DENTA and SPECT had AUC of 0.714, 0.786 and 0.738 respectively. Mean calculated difference of involved height was -0.025 cm by MDCT (p value 0.87), -0.2 cm by OPG (p value 0.09) and 0.12 by DENTA scan (p value 0.41). Mean difference of involved length was -0.51 cm (p value 0.08) and -1.02 cm (p value 0.04) for MDCT and OPG respectively. 50% of tumour invasion was through the occlusal route while large tumours demonstrated multiple routes of entry. CONCLUSION: -Gingivobuccal complex cancers are homogenous with respect to mandibular invasion, preferred route of tumour entry being the occlusal surface. -Multidetector CT scan is fairly accurate in detecting mandibular involvement and predicting extent of involvement. -Oncological safety can be achieved by positioning the bone cuts corresponding to the adjacent soft tissue margins in segmental mandibulectomy.

Assessment of drainage in PUJ dilatation: pelvic excretion efficiency as an index of renal function.

Renal function is important when assessing the response of a dilated renal pelvis to a diuretic stimulus. Yet there is little in the literature to suggest how this should be undertaken. Our aim was to develop a model which we have called pelvic excretion efficiency (PEE). The PEE, which may be used to assess drainage, is a mathematical model of the ratio of the total kidney excretion to the total amount of isotope extracted from the blood by the kidney. Thirty-three children with a prenatal diagnosis of unilateral renal pelvic dilatation (PUJ) were treated conservatively after birth. As a group, they underwent a total of 164 diuretic DTPA renograms up to the age of 72 months. Drainage was assessed as the response to frusemide (defined as the time for the corrected renal curve to fall to 75% of the maximum value in the frusemide part of the study; T75), response to bladder emptying, a change of posture after frusemide (PM), and PEE. The contralateral normal kidney showed a combination of both 'good' T75 and PM drainage in 51% of renograms while the PEE showed drainage in all. The affected kidney with renal pelvic dilatation showed a combination of both 'poor' T75 and PM drainage in 42% of renograms. The PEE was low in 99% of these 'poor drainage' renograms. The PEE, the ratio of the mathematical model of renal uptake to excretion, is readily calculated and may be a more accurate and specific technique to assess drainage on diuretic renography.