Tim Tirrell
Clinical Assistant Professor, Surgery - Pediatric Surgery
All Publications
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Hindgut Duplication in an Infant with Omphalocele-Exstrophy-Imperforate Anus-Spinal Defects (OEIS) Complex.
European journal of pediatric surgery reports
2022; 10 (1): e45-e48
Abstract
Introduction The congenital anomaly of omphalocele, cloacal exstrophy, imperforate anus, and spinal abnormalities (OEIS complex) is rare but well recognized. Hindgut duplications are also uncommon and are not known to be associated with OEIS. We describe a neonate with OEIS who was found to have fully duplicated blind-ending hindguts. Case Report A premature infant boy with OEIS underwent first-stage closure on day of life 6, which included excision of the omphalocele sac, separation of the cecal plate and bladder halves, tubularization of the cecal plate, hindgut rescue with end colostomy, and joining of the bladder halves. Cecal plate inspection revealed two hindgut structures that descended distally, one descended midline into the pelvis along the sacrum and the second laterally along the left border of the sacrum. Both lumens connected to the cecal plate and had separate mesenteries. In an effort to maximize the colonic mucosal surface area, the hindgut segments were unified through a side-to-side anastomosis, creating a larger caliber hindgut. The cecal plate was tubularized and an end colostomy was created. Bowel function returned and he was discharged home on full enteral feeds. Discussion This case represents a cooccurrence of two extremely rare and complex congenital anomalies. The decision to unify the distinct hindguts into a single lumen was made in an effort to combine the goals of management for both OEIS and alimentary duplications. The hindgut is abnormal in OEIS and should be assessed carefully during repair.
View details for DOI 10.1055/s-0041-1742154
View details for PubMedID 35282303
View details for PubMedCentralID PMC8913173
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Technical Considerations in Primary Repair of a Congenital Prostatic Rectourethral Fistula in an Adult-Sized Patient.
European journal of pediatric surgery reports
2022; 10 (1): e20-e24
Abstract
Congenital anorectal malformations are generally diagnosed and repaired as a neonate or infant, but repair is sometimes delayed. Considerations for operative repair change as the patient approaches full stature. We recently encountered a 17-year-old male with an unrepaired congenital rectourethral fistula and detail our experience with his repair. We elected to utilize a combined abdominal and perineal approach, with robotic assistance for division of his rectourethral fistula and pullthrough anoplasty. Cystoscopy was used simultaneously to assure full dissection of the fistula and to minimize the risk of leaving a remnant of the original fistula (also known as a posterior urethral diverticulum). The procedure was well tolerated without complications. His anoplasty was evaluated 60 days postoperatively and was well healed without stricture. At 9 months of follow-up, he has good fecal and urinary continence. Robotic assistance in this procedure allowed minimal perineal dissection while ensuring precise rectourethral fistula dissection. The length of the intramural segment of the fistula was longer than anticipated. Simultaneous cystoscopy, in conjunction with the integrated robotic fluorescence system, helped reduce the risk of leaving a remnant of the original fistula.
View details for DOI 10.1055/s-0041-1742155
View details for PubMedID 35169532
View details for PubMedCentralID PMC8840860
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Contrast enhanced colostography: New applications in preoperative evaluation of anorectal malformations
JOURNAL OF PEDIATRIC SURGERY
2021; 56 (1): 192-195
Abstract
Understanding details of anatomic relationships between the colon and surrounding structures is a critical piece of preoperative planning prior to surgical repair of anorectal malformations (ARMs). Traditional imaging techniques involve ionizing radiation, distention of the rectum with supraphysiologic intraluminal pressures, and sometimes require sedation. Recent developments in the field of contrast agents have allowed the emergence of an ultrasound-based technique that can avoid these requirements while continuing to provide high resolution structural information in three dimensions.Fourteen children (13 male, 1 female, age 1-11 months) with ARMs underwent contrast enhanced colostography (ceCS) in addition to traditional preoperative imaging techniques to delineate anatomic relationships of pelvic structures.ceCS and traditional imaging yielded concordant anatomic information, including structural relationships and fistulous connections, in 10/14 patients (71%). ceCS detected fistulous connection in 2/13 patients (15%) that were not seen by traditional imaging. Ultrasonography failed to detect the fistulous connection in one patient.ceCS is a safe, effective and flexible method for defining important structural information in ARM patients. When compared with traditional methods, it provided equivalent or superior results 93% of the time and bears consideration as a standard tool in preoperative planning for this population.Retrospective Comparative Study.Level III.
View details for DOI 10.1016/j.jpedsurg.2020.09.033
View details for Web of Science ID 000608686400032
View details for PubMedID 33143879
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Safety of delayed surgical repair of omphalocele-exstrophy-imperforate anus-spinal defects (OEIS) complex in infants with significant comorbidities
PEDIATRIC SURGERY INTERNATIONAL
2021; 37 (1): 93-99
Abstract
Management of infants with OEIS complex is challenging and not standardized. Expeditious surgery after birth has been recommended to limit soilage of the urinary tract and optimize intestinal function. However, clinical instability secondary to comorbidities is common in this population and early operation carries risk. We sought to define the risk/benefit profile of delaying repair.All newborn patients with OEIS managed by our institution between Sep 2017 and Oct 2019 were reviewed. Comorbidities were evaluated, including cardiopulmonary pathologies and associated malformations.Ten patients with OEIS were managed. Patients underwent early (2 patients, repair at 0-2 days) or delayed (6 patients, repair at 6-87 days) first-stage exstrophy repair. Two patients died prior to repair (progressive respiratory failure, severe genetic anomalies). Repairs were delayed secondary to cardiac conditions, neurosurgical interventions, medical disease, and/or delayed transfer. Delayed repair patients had longer lengths of stay and use of parenteral nutrition. No patients experienced urinary tract infections prior to repair.Delaying first-stage exstrophy repair to allow physiologic optimization is safe. All repaired patients were discharged home, without parenteral nutrition or supplemental oxygen.
View details for DOI 10.1007/s00383-020-04779-w
View details for Web of Science ID 000592162800001
View details for PubMedID 33231719
View details for PubMedCentralID 1357748
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A New Approach to Cloaca: Laparoscopic Separation of the Urogenital Sinus
JOURNAL OF LAPAROENDOSCOPIC & ADVANCED SURGICAL TECHNIQUES
2020; 30 (12): 1257-1262
Abstract
Introduction: Cloaca malformation repair strategy is strongly dictated by common channel and urethral lengths. Mid to long common channel cloacas are challenging and often require laparotomy for dissection of pelvic structures. The balance of common channel and urethral lengths often dictates the approach for reconstruction. Laparoscopy has been utilized for rectal dissection but not for management of the urogenital (UG) structures. We hypothesized that laparoscopy could be applied to UG separation in reconstruction of cloaca malformations. Methods: Records were reviewed for 9 children with cloaca who underwent laparoscopic rectal mobilization and UG separation. Clinical parameters reviewed included demographics, relevant anatomic lengths, operative duration, transfusion requirements, and perioperative complications. Results: Repair was perfomed at a median (interquartile range) age of 12 (7, 15) months. Common channel length as measured by cystoscopy was 3.5 (3.3, 4.5) cm. There were no intraoperative complications. Transfusion requirements were minimal. Postoperative length of stay was 6 (5, 11) days. One patient developed a urethral web and 2 developed vaginal stenosis. One patient later underwent a laparotomy for obstruction due to a twisted rectal pull-through. Conclusions: Laparoscopic rectal mobilization and UG separation in long common channel cloaca are safe and well tolerated. Laparoscopy affords full evaluation of Mullerian structures and enables separation of the common UG wall, which may ultimately enhance long-term urinary continence.
View details for DOI 10.1089/lap.2020.0641
View details for Web of Science ID 000592656500001
View details for PubMedID 33202165
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Reoperative surgery in anorectal malformation patients
TRANSLATIONAL GASTROENTEROLOGY AND HEPATOLOGY
2021; 6: 43
Abstract
Currently accepted primary repair of congenital anorectal malformations (ARMs) includes a posterior sagittal incision, which allows for optimal visualization and identification of important pelvic structures and anatomical features. Reconstructive surgery involves meticulous dissection and separation of pelvic structures, and careful reconstruction can result in good functional outcomes for many patients, who live without ongoing sequelae from their malformation. However, some patients may require reoperative procedures for anatomic or functional reasons. Males and females present with slightly different symptoms and should be approached differently. Males are most likely to require reoperations for anorectal or urethral pathologies, but the urinary system is often spared in females-they instead must contend with Mullerian duct anomalies, of which there are many varieties. Depending on the original malformation and severity of symptoms, redo surgery may be needed to optimize function and quality of life. Surgical management with reoperative surgery in ARMs ranges from straightforward to complex, depending on the issue. One must weigh the risks of reoperative surgery and potentially creating more scarring against the need for a better anatomical and functional outcome. Current management trends and practice patterns with regards to reoperative surgery in ARM patients are not widely studied or standardized but we provide an overview of the more common pathologies, preoperative evaluation and workup required to identify the issues, and options for reoperative repair in these patients.
View details for DOI 10.21037/tgh-20-214
View details for Web of Science ID 000675467800001
View details for PubMedID 34423164
View details for PubMedCentralID PMC8343547
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Measure twice and cut once: Comparing endoscopy and 3D cloacagram for the common channel and urethral measurements in patients with cloacal malformations
JOURNAL OF PEDIATRIC SURGERY
2020; 55 (2): 257-260
Abstract
Precise and accurate measurement of the common channel and urethra is a critical determinant prior to the repair of cloacal malformations. Endoscopy and 3D reconstruction cloacagram are two common modalities utilized to help plan the surgical approach, however the consistency between these methods is unknown.Common channel and urethral lengths obtained by endoscopy and 3D cloacagram of cloaca patients at six pediatric colorectal centers were compared. Data are given as mean (range).72 patients were included in the study. Common channel measurements determined by 3D cloacagram and endoscopy were equal in 7 cases (10%). Endoscopic measurements of the common channel were longer than 3D cloacagram in 20 (28%) cases and shorter in the remaining 44 (62%) cases. The absolute difference between measurements of the common channel was 7.2 mm (0-2.4 cm). Urethral measurements by both modalities were equal in 8 cases (12%). Endoscopic measurement of the urethra was longer than that by 3D cloacagram in 20 (31%) patients and shorter in 37 (57%) of cases. The absolute difference between measurements of the urethra was 5.1 mm (0-2.0 cm). The reconstruction (e.g. TUM or urogenital separation) that would be performed according to measurements determined by 3D cloacagram and endoscopic measurements differed in 13/62 (21%) patients with each structure identified and common channel measurements of >1 cm.Significant variation exists in the measurements of the common channel and urethra in patients with cloacal malformations as determined by endoscopy and 3D cloacagram. This variation should be considered as these measurements influence the decision to perform either a TUM or urogenital separation. Based on these findings, 3D cloacagram should be performed in all patients prior to cloaca repair to prevent mischaracterization of the malformation.Level IV.
View details for DOI 10.1016/j.jpedsurg.2019.10.045
View details for Web of Science ID 000510865200011
View details for PubMedID 31784103
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Analysis of hierarchical biomechanical data structures using mixed-effects models
JOURNAL OF BIOMECHANICS
2018; 69: 34-39
Abstract
Rigorous statistical analysis of biomechanical data is required to understand tissue properties. In biomechanics, samples are often obtained from multiple biopsies in the same individual, multiple samples tested per biopsy, and multiple tests performed per sample. The easiest way to analyze this hierarchical design is to simply calculate the grand mean of all samples tested. However, this may lead to incorrect inferences. In this report, three different analytical approaches are described with respect to the analysis of hierarchical data obtained from muscle biopsies. Each method was used to analyze an actual experimental data set obtained from muscle biopsies of three different muscles in the human forearm. The results illustrate the conditions under which mixed-models or simple models are acceptable for analysis of these types of data.
View details for DOI 10.1016/j.jbiomech.2018.01.013
View details for Web of Science ID 000426229300005
View details for PubMedID 29366561
View details for PubMedCentralID PMC5913736
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Lymph node assessment and survival: we still have work to do
JOURNAL OF THORACIC DISEASE
2018; 10 (1): 15-16
View details for DOI 10.21037/jtd.2017.12.112
View details for Web of Science ID 000425262600029
View details for PubMedID 29600011
View details for PubMedCentralID PMC5863158
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The mechanical strength of side-to-side tendon repair with mismatched tendon size and shape
JOURNAL OF HAND SURGERY-EUROPEAN VOLUME
2015; 40 (3): 239-245
Abstract
Tendon transfers frequently require coaptation of two mismatched tendons. In this cadaver study, ultimate load, stiffness, and Young's modulus were measured in tendon-to-tendon attachments with mismatched donor and recipient tendons, using pronator teres (PT) to extensor carpi radialis brevis (ECRB) and flexor carpi ulnaris (FCU) to extensor digitorum communis (EDC). FCU-to-EDC attachments failed at higher loads than PT-to-ECRB attachments, but they had similar modulus and stiffness values. Ultimate tensile strength of the tendon attachments exceeded the maximum predicted contraction force of any of the transferred muscles, with safety factors of four-fold for the FCU-to-EDC and two-fold for the PT-to-ECRB transfers. This implies that size and shape mismatches should not be contraindications to tendon attachment in transfers. The strength safety factors suggest that postoperative immobilization of these transfers is unnecessary.
View details for DOI 10.1177/1753193413517327
View details for Web of Science ID 000350118500003
View details for PubMedID 24413573
View details for PubMedCentralID PMC4366193
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Functional Consequence of Distal Brachioradialis Tendon Release: A Biomechanical Study
JOURNAL OF HAND SURGERY-AMERICAN VOLUME
2013; 38A (5): 920-926
Abstract
Open reduction and internal fixation of distal radius fractures often necessitates release of the brachioradialis from the radial styloid. However, this common procedure has the potential to decrease elbow flexion strength. To determine the potential morbidity associated with brachioradialis release, we measured the change in elbow torque as a function of incremental release of the brachioradialis insertion footprint.In 5 upper extremity cadaveric specimens, we systematically released the brachioradialis tendon from the radius and measured the resultant effect on brachioradialis elbow flexion torque. We defined release distance as the distance between the release point and the tip of the radial styloid.Brachioradialis elbow flexion torque dropped to 95%, 90%, and 86% of its original value at release distances of 27, 46, and 52 mm, respectively. Importantly, brachioradialis torque remained above 80% of its original value at release distances up to 7 cm.Our data demonstrate that release of the brachioradialis tendon from its insertion has minor effects on its ability to transmit force to the distal radius.These data imply that release of the distal brachioradialis tendon during distal radius open reduction internal fixation can be performed without meaningful functional consequences to elbow flexion torque. Even at large release distances, overall elbow flexion torque loss after brachioradialis release would be expected to be less than 5% because of the much larger contributions of the biceps and brachialis. Use of the brachioradialis as a tendon transfer donor should not be limited by concerns of elbow flexion loss, and the tendon could be considered as an autograft donor.
View details for DOI 10.1016/j.jhsa.2013.01.029
View details for Web of Science ID 000318581100012
View details for PubMedID 23528425
View details for PubMedCentralID PMC3640432
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Mobile Tablet Use among Academic Physicians and Trainees
JOURNAL OF MEDICAL SYSTEMS
2013; 37 (1): 9903
Abstract
The rapid adoption rate and integration of mobile technology (tablet computing devices and smartphones) by physicians is reshaping the current clinical landscape. These devices have sparked an evolution in a variety of arenas, including educational media dissemination, remote patient data access and point of care applications. Quantifying usage patterns of clinical applications of mobile technology is of interest to understand how these technologies are shaping current clinical care. A digital survey examining mobile tablet and associated application usage was administered via email to all ACGME training programs. Data regarding respondent specialty, level of training, and habits of tablet usage were collected and analyzed. 40% of respondents used a tablet, of which the iPad was the most popular. Nearly half of the tablet owners reported using the tablet in clinical settings; the most commonly used application types were point of care and electronic medical record access. Increased level of training was associated with decreased support for mobile computing improving physician capabilities and patient interactions. There was strong and consistent desire for institutional support of mobile computing and integration of mobile computing technology into medical education. While many physicians are currently purchasing mobile devices, often without institutional support, successful integration of these devices into the clinical setting is still developing. Potential reasons behind the low adoption rate may include interference of technology in doctor-patient interactions or the lack of appropriate applications available for download. However, the results convincingly demonstrate that physicians recognize a potential utility in mobile computing, indicated by their desire for institutional support and integration of mobile technology into medical education. It is likely that the use of tablet computers in clinical practice will expand in the future. Thus, we believe medical institutions, providers, educators, and developers should collaborate in ways that enhance the efficacy, reliability, and safety of integrating these devices into daily medical practice.
View details for DOI 10.1007/s10916-012-9903-6
View details for Web of Science ID 000315681600005
View details for PubMedID 23321961
View details for PubMedCentralID PMC4057035
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Smartphone App Use Among Medical Providers in ACGME Training Programs
JOURNAL OF MEDICAL SYSTEMS
2012; 36 (5): 3135-3139
Abstract
The past decade has witnessed the advent of the smartphone, a device armed with computing power, mobility and downloadable "apps," that has become commonplace within the medical field as both a personal and professional tool. The popularity of medically-related apps suggests that physicians use mobile technology to assist with clinical decision making, yet usage patterns have never been quantified. A digital survey examining smartphone and associated app usage was administered via email to all ACGME training programs. Data regarding respondent specialty, level of training, use of smartphones, use of smartphone apps, desired apps, and commonly used apps were collected and analyzed. Greater than 85% of respondents used a smartphone, of which the iPhone was the most popular (56%). Over half of the respondents reported using apps in their clinical practice; the most commonly used app types were drug guides (79%), medical calculators (18%), coding and billing apps (4%) and pregnancy wheels (4%). The most frequently requested app types were textbook/reference materials (average response: 55%), classification/treatment algorithms (46%) and general medical knowledge (43%). The clinical use of smartphones and apps will likely continue to increase, and we have demonstrated an absence of high-quality and popular apps despite a strong desire among physicians and trainees. This information should be used to guide the development of future healthcare delivery systems; expanded app functionality is almost certain but reliability and ease of use will likely remain major factors in determining the successful integration of apps into clinical practice.
View details for DOI 10.1007/s10916-011-9798-7
View details for Web of Science ID 000307994400042
View details for PubMedID 22052129
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Human skeletal muscle biochemical diversity
JOURNAL OF EXPERIMENTAL BIOLOGY
2012; 215 (15): 2551-2559
Abstract
The molecular components largely responsible for muscle attributes such as passive tension development (titin and collagen), active tension development (myosin heavy chain, MHC) and mechanosensitive signaling (titin) have been well studied in animals but less is known about their roles in humans. The purpose of this study was to perform a comprehensive analysis of titin, collagen and MHC isoform distributions in a large number of human muscles, to search for common themes and trends in the muscular organization of the human body. In this study, 599 biopsies were obtained from six human cadaveric donors (mean age 83 years). Three assays were performed on each biopsy - titin molecular mass determination, hydroxyproline content (a surrogate for collagen content) and MHC isoform distribution. Titin molecular mass was increased in more distal muscles of the upper and lower limbs. This trend was also observed for collagen. Percentage MHC-1 data followed a pattern similar to collagen in muscles of the upper extremity but this trend was reversed in the lower extremity. Titin molecular mass was the best predictor of anatomical region and muscle functional group. On average, human muscles had more slow myosin than other mammals. Also, larger titins were generally associated with faster muscles. These trends suggest that distal muscles should have higher passive tension than proximal ones, and that titin size variability may potentially act to 'tune' the protein's mechanotransduction capability.
View details for DOI 10.1242/jeb.069385
View details for Web of Science ID 000306605200010
View details for PubMedID 22786631
View details for PubMedCentralID PMC3394665
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Moment arms of the human digital flexors
JOURNAL OF BIOMECHANICS
2011; 44 (10): 1987-1990
Abstract
For the extrinsic hand flexors (flexor digitorum profundus, FDP; flexor digitorum superficialis, FDS; flexor pollicis longus, FPL), moment arm corresponds to the tendon's distance from the center of the metacarpalphalangeal (MP), proximal interphalangeal (PIP), or distal interphalangeal (DIP) joint. The clinical value of establishing accurate moment arms has been highlighted for biomechanical modeling, the development of robotic hands, designing rehabilitation protocols, and repairing flexor tendon pulleys (Brand et al., 1975; An et al., 1983; Thompson and Giurintano, 1989; Deshpande et al., 2010; Wu et al., 2010). In this study, we define the moment arms for all of the extrinsic flexor tendons of the hand across all digital joints for all digits in cadaveric hands.
View details for DOI 10.1016/j.jbiomech.2011.04.025
View details for Web of Science ID 000293048000023
View details for PubMedID 21561624
View details for PubMedCentralID PMC3124620
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Resonance Raman Studies of the (His)(Cys)<sub>3</sub> 2Fe-2S Cluster of MitoNEET: Comparison to the (Cys)<sub>4</sub> Mutant and Implications of the Effects of pH on the Labile Metal Center
BIOCHEMISTRY
2009; 48 (22): 4747-4752
Abstract
MitoNEET is a 2Fe-2S outer mitochondrial membrane protein that was initially identified as a target for anti-diabetic drugs. It exhibits a novel protein fold, and in contrast to other 2Fe-2S proteins such as Rieske proteins and ferredoxins, the metal clusters in the mitoNEET homodimer are each coordinated by one histidine residue and three cysteine residues. The interaction of the ligating His87 residue with the 2Fe-2S moiety is especially significant because previous studies have shown that replacement with Cys in the H87C mutant stabilizes the cluster against release. Here, we report the resonance Raman spectra of this naturally occurring Fe(2)S(2)(His)(Cys)(3) protein to assess local structural changes associated with cluster lability. Comparison of mitoNEET to its ferredoxin-like H87C mutant indicates that Raman peaks in the approximately 250-300 cm(-1) region of mitoNEET are influenced by the Fe-His87 moiety. Systematic pH-dependent resonance Raman spectral changes were observed in this spectral region for native mitoNEET but not the H87C mutant. The approximately 250-300 cm(-1) region of native mitoNEET is also sensitive to phosphate buffer. Thus, conditions that influence cluster release are shown here to concomitantly affect the resonance Raman spectrum in the region with Fe-His contribution. These results support the hypothesis that the Fe-N(His87) interaction is modulated within the physiological pH range, and this modulation may be critical to the function of mitoNEET.
View details for DOI 10.1021/bi900028r
View details for Web of Science ID 000266601500010
View details for PubMedID 19388667
View details for PubMedCentralID PMC2861891
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Cyclometalated iridium(III)-sensitized titanium dioxide solar cells
PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES
2006; 5 (10): 871-873
Abstract
Ir(III) dyes used as sensitizers in dye-sensitized solar cells produced quantum yields approaching unity for conversion of absorbed photons to current under simulated air mass 1.0 sunlight, with current production resulting from ligand-to-ligand charge-transfer states, rather than the typical metal-to-ligand charge-transfer states in ruthenium-based cells.
View details for DOI 10.1039/b608430c
View details for Web of Science ID 000240999400002
View details for PubMedID 17019464