Microtomographic Analysis of Lower Urinary Tract Obstruction

Abstract

Prenatal obstruction of the lower urinary tract may result in megacystis, with subsequent development of hydro-ureter, hydronephrosis, and renal damage. Oligo- or anhydramnios, pulmonary hypoplasia, and prune belly syndrome are lethal consequences. Causes and mechanisms responsible for obstruction remain unclear but might be clarified by anatomic study at autopsy. To this end, we employed 2 methods of tomographic imaging—optical projection tomography and contrast-enhanced microCT scanning—to elucidate the anatomy of the intact urinary bladder and urethra in 10 male fetuses with lower urinary tract obstruction. Images were compared with those from 9 age-matched controls. Three-dimensional images, rotated and sectioned digitally in multiple planes, permitted thorough examination while preserving specimens for later study. Both external and internal features of the bladder and urethra were demonstrated; small structures (ie, urethral crest, verumontanum, prostatic utricle, ejaculatory ducts) were seen in detail. Types of obstruction consisted of urethral atresia (n = 5), severe urethral stenosis (n = 2), urethral diaphragm (n = 2), or physical kinking (n = 1); classic (Young type I) posterior urethral valves were not encountered. Traditional light microscopy was then used to verify tomographic findings. The prostate gland was hypoplastic or absent in all cases; in 1, prostatic tissue was displaced inferior to the verumontanum. Findings support previous views that dissection may produce valve-like artifacts (eg, bisection of an obstructing diaphragm) and that deformation of an otherwise normal urethra may result in megacystis. The designation “posterior urethral valves” should not be used as a generic expression of urethral obstruction unless actual valves are demonstrated.

Early clinical applications for imaging at microscopic detail: microfocus computed tomography (micro-CT)

“…Imaging of a multicystic dysplastic kidney revealed cysts of varying sizes with histological confirmation. Another study demonstrated imaging of lower urinary tract obstruction using contrast-enhanced micro-CT. 49 Cystic kidney disorders have variable inheritance patterns, with a wide variation in recurrence risk. With further optimization, micro-CT may be able to provide a non-invasive, permanent record of disease phenotype in such cases without the need for a full autopsy.…”

Biometric and morphological features on magnetic resonance imaging of fetal bladder in lower urinary tract obstruction: new perspectives for fetal cystoscopy

“…The main strength of this study is the in‐vivo nature of the measurements and our novel approach to the future development of fetal‐therapy instruments. Studying the intact urinary tract (as opposed to postmortem work‐ups 11 ) in vivo preserves its true shape and anatomical relationships to other pelvic organs, and therefore gives real clinical meaning to the biometric study. The main technical limitation of this study is the small number of cases.…”

Differences in Oral Structure and Tissue Interactions during Mouse vs. Human Palatogenesis: Implications for the Translation of Findings from Mice

“…Standard settings were used for imaging of craniofacial bones (Vora et al, 2016 ). For human soft tissue imaging using the microCT, tissues were first stained with PTAH (phosphotungstic acid-hematoxylin) as previously described (Siebert et al, 2013 ). Raw OPT and microCT scan data were reconstructed using NRecon V1.6.9.4 software (Skyscan, Belgium) and imported into the Drishti Volume Exploration software V 2.6.1 for 3D rendering and image capture.…”