Linking reduced breaking crest speeds to unsteady nonlinear water wave group behavior.

Observed crest speeds of maximally steep, breaking water waves are much slower than expected. Our fully nonlinear computations of unsteadily propagating deep water wave groups show that each wave crest approaching its maximum height slows down significantly and either breaks at this reduced speed, or accelerates forward unbroken. This previously noted crest slowdown behavior was validated as generic in our extensive laboratory and field observations. It is likely to occur in unsteady dispersive nonlinear wave groups in other natural systems.

Adhaeribacter aquaticus gen. nov., sp. nov., a Gram-negative isolate from a potable water biofilm.

A Gram-negative bacterium was isolated from a freshwater biofilm developed on a stainless steel surface under a fluid velocity of 0.26 m s(-1). The strain, MBRG1.5(T), was cultivated on R2A agar and formed pink colonies. Light microscopy and negative staining in a transmission electron microscope showed that the cells were rod-shaped, approximately 2.8-4.1 microm long by 0.9-1.7 microm wide in size and produced large quantities of extracellular fibrillar material. Additionally, following growth in batch culture, transmission electron microscopy showed that many cells plasmolysed. Stationary-phase cells were more variable in size and shape. The DNA G+C content was 40.0 mol%. The most abundant fatty acids were 15 : 0 iso (22.5 %), followed by 16 : 1omega5c (16.9 %) and 15 : 0 iso 2-OH (16.5 %). Phylogenetic analysis of the 16S rRNA gene showed that the strain was a member of the family 'Flexibacteraceae' of the Cytophaga-Flavobacterium-Bacteroides group. Phenotypic and genotypic analyses indicated that the strain could not be assigned to any recognized genus; therefore a novel genus and species, Adhaeribacter aquaticus gen. nov., sp. nov., is proposed, with MBRG1.5(T) (=DSM 16391(T)=NCIMB 14008(T)) as the type strain.

MR imaging of the penis.

The signal intensity of the corpora cavernosa of the penis at magnetic resonance (MR) imaging may vary from that of the corpus spongiosum; this difference is dependent on the rate of blood flow within the cavernous spaces that constitute the corporal bodies. Also visible at MR imaging are the layers of fibrous tissue that envelop the corporal bodies, the deep arteries and veins, subcutaneous connective tissue, tunica dartos, epidermis, and urethra. While the iliac, pudendal, perineal, and common penile arteries can be evaluated with three-dimensional MR angiography, the smaller end arteries of the penis have not yet been reliably demonstrated. MR imaging may be used to detect and stage penile and urethral cancers, identify and characterize benign penile masses, evaluate arteriogenic impotence, identify penile fractures, evaluate penile prostheses, localize periurethral abscesses, and identify plaques of Peyronie disease. With its direct multiplanar imaging capabilities, superb soft-tissue contrast, and excellent spatial resolution, high-field surface coil MR imaging can show the soft-tissue and vascular anatomy of the penis, as well as the appearance of many penile diseases.

Nitric oxide inhalation increases alveolar gas exchange by decreasing deadspace volume.

OBJECTIVE: To test the hypothesis that nitric oxide inhalation facilitates CO2 elimination by decreasing alveolar deadspace in an ovine model of acute lung injury. DESIGN: Prospective, placebo-controlled, randomized, crossover model. SETTING: University research laboratory. SUBJECTS: Eleven mixed-breed adult sheep. INTERVENTIONS: To induce acute lung injury, hydrochloric acid was instilled into the tracheas of paralyzed sheep receiving controlled mechanical ventilation. Each sheep breathed 0 ppm, 5 ppm, and 20 ppm nitric oxide in random order. MEASUREMENTS AND MAIN RESULTS: Estimates of alveolar deadspace volumes and arterial-to-end tidal CO2 partial pressure differences were used as indicators of CO2 elimination efficiency. At a constant minute ventilation, nitric oxide inhalation caused dose-independent decreases in Paco2 (p <.05), alveolar deadspace (p <.01), and arterial-to-end tidal CO2 partial pressure differences (p <.01). We found that estimates of arterial-to-end tidal CO2 partial pressure differences may be used to predict alveolar deadspace volume (r2 =.86, p <.05). CONCLUSIONS: Estimates of arterial-to-end tidal CO2 partial pressure differences are reliable indicators of alveolar deadspace. Both values decreased during nitric oxide inhalation in our model of acutely injured lungs. This finding supports the idea that nitric oxide inhalation facilitates CO2 elimination in acutely injured lungs. Future studies are needed to determine whether nitric oxide therapy can be used to reduce the work of breathing in selected patients with cardiopulmonary disorders.

Simultaneous upper and lower urinary tract obstruction associated with severe genital prolapse: diagnosis and evaluation with magnetic resonance imaging.

Genital prolapse causing both urethral and ureteral obstruction is an infrequent occurrence, especially in the absence of uterine prolapse. We report on a patient with massive genital prolapse causing both urethral and ureteral obstruction in whom magnetic resonance imaging demonstrated the level of obstructive uropathy and, after surgical repair of the prolapse, confirmed restoration of the normal pelvic and upper urinary tract anatomy.

Endoluminal magnetic resonance imaging in the evaluation of urethral diverticula in women.

OBJECTIVES: Accurate determination of the size and extent of urethral diverticula can be important in planning operative reconstruction and repair. Voiding cystourethrography (VCUG) is currently the most commonly used study in the preoperative evaluation of urethral diverticula. We reviewed our experience with the use of endoluminal (endorectal or endovaginal) magnetic resonance imaging (eMRI) in these patients as an adjunctive study to VCUG to evaluate whether the MRI provided anatomically important information that was not apparent on VCUG. METHODS: A retrospective analysis of all patients with a clinical diagnosis of urethral diverticula undergoing MRI at a single institution was performed. Patients were evaluated with history, physical examination, cystoscopy, VCUG, and eMRI. Endoluminal MRI was retrospectively compared to VCUG with respect to size, extent, and location found at operative exploration. RESULTS: Twenty-seven consecutive patients underwent endorectal or endovaginal coil MRI in the evaluation of suspected urethral diverticula. Twenty patients subsequently had attempted transvaginal operative repair of the diverticulum. In 2 patients, eMRI demonstrated a urethral diverticulum, whereas VCUG did not. Operative exploration in these patients revealed a urethral diverticulum. In 14 of 27 patients, the VCUG underestimated the size and complexity of the urethral diverticulum as compared to eMRI and operative exploration. In 13 of 27 patients, the size, location, and extent of the urethral diverticulum on VCUG correlated well with the eMRI and/or operative findings. CONCLUSIONS: We have found endorectal and endovaginal coil MRI to be extremely accurate in determining the size and extent of urethral diverticula as compared to VCUG. This information can be critical when planning the approach, dissection, and reconstruction of these sometimes complex cases.

Urologic complications of Crohn's disease.

Crohn's disease frequently can affect the genitourinary system, mainly in the form of urinary fistulae and urolithiasis. Diagnostic evaluation of fistulae associated with Crohn's disease has improved with the increasing use of computed tomography and MR imaging, along with other diagnostic modalities. Resective surgery is the main treatment in this group of patients. Kidney stones are common because of metabolic derangements and dehydration; however, these can be treated adequately with minimally invasive procedures, such as extracorporeal shock-wave lithotripsy, ureteroscopy, and percutaneous surgery. In addition, medical therapies can prevent recurrent stones.

Injected periurethral collagen for postprostatectomy urinary incontinence: MR and CT appearance.

BACKGROUND: Urinary incontinence, a disturbing complication of radical prostatectomy, is often treated with periurethral collagen injections to increase urethral closure and resistance to urinary outflow. METHODS: Using magnetic resonance imaging and computed tomography, we studied the appearance of glutaraldehyde cross-lined bovine collagen endoscopically injected into the periurethral tissues in four men who developed urinary incontinence after radical prostatectomy. Collagen was also scanned in vitro to verify its magnetic resonance appearance. RESULTS: Collagen deposits appear as well-circumscribed nodules of low to intermediate signal intensity on both T1- and T2-weighted images in the periurethral tissues or in the base of the subjacent penile bulb (base of corpus spongiosum). On contrast-enhanced computed tomography, collagen appears as a hypoattenuating nodular-filling defect within the penile bulb. CONCLUSION: These imaging characteristics should allow differentiation of collagen from locally recurrent prostate carcinoma and avoid inappropriate work-up of benign findings.

Imaging urologic complications of pancreas transplantation with bladder drainage.

Urologic complications of bladder-drained pancreas transplants include cystitis, duodenitis and urethritis; duodenal ulceration and perforation; and periallograft fluid collections. These complications are readily depicted radiographically, and their recognition may be crucial for patient management.

Tracheal pressure ventilator control.

Tracheal pressure ventilator control (TPVC) is a ventilator mode that relies on tracheal pressure at the carinal end of the endotracheal tube for triggering the ventilator ;;on,'' controlling pressure, and cycling the ventilator ;;off.'' TPVC automatically nullifies imposed resistive work of the breathing apparatus (endotracheal tube plus ventilator) by providing automatic and variable levels of pressure assist. TPVC improves ventilator responsiveness for a spontaneously breathing patient by providing significantly higher peak inspiratory flow rates much closer to that demanded by a patient. TPVC also provides higher assist pressures and flow rates earlier in the breath and thus better-match ventilator-supplied flow to patient-demanded flow than an equivalent level of pressure support ventilation. Matching patient demand for flow to ventilator supply of flow, early in the breath, promotes patient-ventilator synchrony and minimizes work of breathing. We recommend moving the pressure-triggering and control site to the carinal end of the endotracheal tube to provide TPVC.

Ventral hernia of the urinary bladder with mixed urinary incontinence: treatment with herniorrhaphy and allograft fascial sling.

Abdominal hernias are not rare in women with urinary incontinence, but incisional bladder hernia is uncommon. The presenting symptoms in the rare cases reported included suprapubic discomfort, irritative voiding symptoms, and urinary incontinence. We present a patient with bladder herniation and severe mixed urinary incontinence. The pathophysiology of the urinary symptoms and the surgical alternatives for the correction of this condition are discussed.

Angiomyolipoma of the renal sinus: diagnosis by percutaneous biopsy.

We report a case of angiomyolipoma of the renal sinus discovered incidentally during an evaluation for microscopic hematuria. Diagnosis was confirmed by percutaneous aspiration biopsy performed with magnetic resonance imaging control allowing differentiation of this entity from other fatty tumors of the renal sinus including liposarcoma, lipoma, and sinus lipomatosis.

Epidermoid cysts of the testicle: sonographic and MR imaging features.

OBJECTIVE: The purpose of this study is to analyze the appearance of testicular epidermoid cysts on high-resolution sonography and MR imaging and correlate imaging features with histopathologic findings. CONCLUSION: Intratesticular epidermoid cysts may show imaging features that correlate with their histopathologic findings. Concentric rings of alternating hypo- and hyperechogenicity on sonography and alternating high and low signal intensity on MR imaging ("onion ring" appearance) correspond to the pathologic finding of multiple layers of keratin debris. Absence of flow on color Doppler sonography and absence of contrast enhancement on MR imaging is also consistent with the avascular nature of these lesions. The ability of preoperative imaging studies to suggest the diagnosis of epidermoid cyst may prompt a testis-sparing surgery instead of an orchiectomy.

Renal neoplasms amenable to partial nephrectomy: MR imaging.

PURPOSE: To determine the magnetic resonance (MR) imaging characteristics of renal lesions in patients who undergo technically successful partial nephrectomy. MATERIALS AND METHODS: Between February 1991 and September 1997, 38 patients (41 lesions) who underwent partial nephrectomy at a single institution were preoperatively evaluated with contrast material-enhanced, multiplanar, surface-coil MR imaging. Imaging findings that could affect the decision to perform partial nephrectomy were retrospectively evaluated: tumor size; tumor location; presence of pseudocapsule; suspected tumor invasion of renal sinus fat, renal collecting system, renal vein, or perinephric fat; and morphologic and physiologic status of the contralateral kidney. Correlation was made with surgical and pathologic findings. RESULTS: Thirty-three of 41 lesions (80%) were renal cell carcinomas, five were oncocytic neoplasms (12%), two were hemorrhagic cysts (5%), and one was an angiomyolipoma (2%). Twenty-four of 41 (59%) lesions had pseudocapsules. In most cases, the perinephric fat (n = 38 [93%]), the renal sinus fat (n = 31 [76%]), and the renal collecting system (n = 39 [95%]) were correctly interpreted as being uninvolved by tumor. CONCLUSION: Renal neoplasms amenable to partial nephrectomy can be identified and characterized with contrast-enhanced, multiplanar, surface-coil MR imaging.

Respiratory system compliance decreases after cardiopulmonary resuscitation and stomach inflation: impact of large and small tidal volumes on calculated peak airway pressure.

The purpose of the present study was to evaluate respiratory system compliance after cardiopulmonary resuscitation (CPR) and subsequent stomach inflation. Further, we calculated peak airway pressure according to the different tidal volume recommendations of the European Resuscitation Council (7.5 ml/kg) and the American Heart Association (15 ml/kg) for ventilation of an unintubated cardiac arrest victim. After 4 min of ventricular fibrillation, and 6 min of CPR, return of spontaneous circulation (ROSC) after defibrillation occurred in seven pigs. Respiratory system compliance was measured at prearrest, after ROSC, and after 2 and 4 l of stomach inflation in the postresuscitation phase; peak airway pressure was subsequently calculated. Before cardiac arrest the mean (+/- S.D.) respiratory system compliance was 30 +/- 3 ml/cm H2O, and decreased significantly (P < 0.05) after ROSC to 24 +/- 5 ml/cm H2O, and further declined significantly to 18 +/- 4 ml/cm H2O after 2 l, and to 13 +/- 3 ml/cm H2O after 4 l of stomach inflation. At prearrest, the mean +/- S.D. calculated peak airway pressure according to European versus American guidelines was 9 +/- 1 versus 18 +/- 3 cm H2O, after ROSC 12 +/- 2 versus 23 +/- 4 cm H2O, and 15 +/- 2 versus 30 +/- 5 cm H2O after 2 l, and 22 +/- 6 versus 44 +/- 12 cm H2O after 4 l of stomach inflation. In conclusion, respiratory system compliance decreased significantly after CPR and subsequent induction of stomach inflation in an animal model with a wide open airway. This may have a significant impact on peak airway pressure and distribution of gas during ventilation of an unintubated patient with cardiac arrest.

Propagation of nitric oxide pools during controlled mechanical ventilation.

OBJECTIVE: Infusing nitric oxide at a constant rate into a breathing circuit with intermittent mainstream flow causes formation of nitric oxide pools between successive breaths. We hypothesized that incomplete mixing of these pools can confound estimates of delivered nitric oxide concentrations. METHODS: Nitric oxide flowed at a constant rate into the upstream end of a standard adult breathing circuit connected to a lung model. One-milliliter gas samples were obtained from various sites within the breathing system and during various phases of the breathing cycle. These samples were aspirated periodically by a microprocessor controlled apparatus and analyzed using an electrochemical sensor. RESULTS: The pools of nitric oxide distorted into hollow parabolic cone shapes and remained unmixed during their propagation into the lungs. In our preparation, time-averaged nitric oxide concentrations were minimal 60 cm downstream of the infusion site (18 ppm) and maximal 15 cm upstream of the Y-piece (36 ppm). The concentrations were mid-range within the lung (23 ppm), yet were substantially less than predicted by assuming homogeneity of the gases (31 ppm). Generally, nitric oxide concentrations within the lung were different from all other sites tested. CONCLUSION: Incomplete mixing of nitric oxide confounds estimates of delivered nitric oxide concentrations. When nitric oxide is infused at a constant rate into a breathing circuit, we doubt that any sampling site outside the patient's lungs can reliably predict delivered nitric oxide concentrations. Strategies to ensure complete mixing and representative sampling of nitric oxide should be considered carefully when designing nitric oxide delivery systems.