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S J Knechtle

Publications and source records attributed to S J Knechtle.

At least 37 records · Page 2Linked to original sources

Simultaneous pancreas-kidney transplantation and living related donor renal transplantation in patients with diabetes: is there a difference in survival?

OBJECTIVE: To compare the outcome of simultaneous pancreas-kidney transplantation (SPK) and living related donor renal transplantation (LRD) in patients with diabetes. SUMMARY BACKGROUND DATA: It remains unanswered whether diabetic patients with end-stage renal failure are better served by LRD or SPK. METHODS: Using a longitudinal database, data from all diabetic patients receiving LRD or cadaveric renal transplants or SPKs from January 1986 through January 1996 were analyzed. Patient and graft survival, early graft function, and the cause of patient and graft loss were compared for 43 HLA-identical LRDs, 87 haplotype-identical LRDs, 379 SPKs, and 296 cadaveric renal transplants. RESULTS: The demographic composition of the SPK and LRD groups were similar, but because of less strict selection criteria in the cadaveric transplant group, patients were 10 years older, more patients received dialysis, and patients had been receiving dialysis longer before transplantation. Patient survival was similar for the SPK and LRD groups but was significantly lower for the cadaveric renal transplant group. Similarly, there was no difference in graft survival between SPK and LRD recipients, but it was significantly lower for recipients in the cadaveric renal transplant group. Delayed graft function was significantly more common in the cadaveric renal transplant group. Discharge creatinine, the strongest predictor of patient and graft survival, was highest in the SPK group and lowest in the HLA-identical LRD group. The rate of rejection within the first year was greatest in SPK patients (77%), intermediate in the haplotype-identical LRD and cadaveric transplant groups (57% and 48%, respectively), and lowest (16%) in the HLA-identical LRD group. Cardiovascular disease was the primary cause of death for all groups. Acute rejection, chronic rejection, and death with a functioning graft were the predominant causes of graft loss. CONCLUSIONS: This study demonstrates that there was no difference in patient or graft survival in diabetic patients receiving LRD or SPK transplants. However, graft and patient survival rates in diabetic recipients of cadaveric renal transplants were significantly lower than in the other groups.

Adult↗

T cell activation up-regulates the expression of the focal adhesion kinase Pyk2: opposing roles for the activation of protein kinase C and the increase in intracellular Ca2+.

T cell activation initiates signals that control gene expression of molecules important for T cell function. The focal adhesion kinase Pyk2 has been implicated in T cell signaling. To further analyze the involvement of Pyk2 in T cell processes, we examined the effect of T cell stimulation on the expression of Pyk2. We found that TCR ligation or PMA increased Pyk2 expression in Jurkat T cells and in normal T cells. In contrast, TCR ligation and PMA failed to induce any detectable increase in the expression of the other member of the focal adhesion kinase family, Fak, in Jurkat T cells and induced only a weak increase in Fak expression in normal T cells. The serine/threonine kinases, protein kinase C and mitogen-activated protein/extracellular signal-related kinase kinase (MEK), regulated Pyk2 expression, as inhibitors of these kinases blocked stimulus-induced Pyk2 expression. Cyclosporin A, FK506, and KN-62 did not block Pyk2 expression; thus, calcineurin and Ca2+/calmodulin-activated kinases are not critical for augmenting Pyk2 expression. TCR ligation increased Pyk2 mRNA, and the transcriptional inhibitor actinomycin D blocked Pyk2 expression. Strikingly, Ca2+ ionophores, at concentrations that in combination with other stimuli induced IL-2 expression, blocked TCR- and PMA-induced up-regulation of Pyk2 expression. Thus, the increase in Ca2+ has opposing effects on IL-2 and Pyk2 expression. Cyclosporin A and FK506, but not KN-62, blocked Ca2+ ionophore-mediated inhibition of Pyk2 expression, implicating calcineurin in down-regulating Pyk2 expression. These results show that TCR-triggered intracellular signals increase Pyk2 expression and shed light on the molecular mechanisms that regulate Pyk2 expression in T cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

The impact of hypoalbuminemia in kidney-pancreas transplant recipients.

BACKGROUND: Hypoalbuminemia is associated with poorer outcomes in renal transplantation. Diabetes can compound hypoalbuminemia's detrimental effects. Kidney-pancreas transplantation alters the diabetic milieu; yet, some patients continue to be hypoalbuminemic. METHODS: We retrospectively analyzed 232 patients who underwent simultaneous kidney-pancreas transplantation (SPK) between 1993 and 1997 to determine the incidence and clinical correlates of hypoalbuminemia in SPK recipients. Post-SPK hypoalbuminemia was defined as a serum albumin level < or =3.5 g/dl. Univariate analyses were performed to determine whether post-SPK hypoalbuminemia was associated with pre-SPK variables. The effect of albumin level and hypoalbuminemia on the risk of post-SPK events (cardiac events, cytomegalovirus [CMV] infection, rejection, readmission, kidney and pancreas graft failure, and death) was examined with a Cox proportional hazards model. RESULTS: The study population consisted of 149 men and 83 women. Average follow-up was 2.0+/-1.3 years. Hypoalbuminemia (serum albumin level < or =3.5 g/dL) was most common early after SPK (3 months: 44% of evaluable patients were hypoalbuminemic; 12 months: 15.3%; 36 months: 8.3%). Acute rejection episodes and readmission were the most common adverse events after SPK transplantation. There were 24 episodes of renal allograft loss and only 5 cardiac events. Ten SPK recipients died during the study time period. SPK-related hypoalbuminemia was associated with an increased risk for CMV infection (risk ratio [RR] 2.5; P<0.02), renal graft failure (RR 2.41; P=0.05), pancreas graft failure (RR 3.66; P=0.01), and a trend toward an increased risk for death (RR 2.8; P=0.19). CONCLUSIONS: Post-SPK hypoalbuminemia resolves over time in many patients. Persistent post-SPK hypoalbuminemia is associated with an increased risk for CMV infection, graft loss, and a trend toward decreased survival. Efforts to improve nutrition, as it may affect hypoalbuminemia in SPK recipients, may be one strategy for improving SPK outcomes.

Aged↗

Iliac artery pseudoaneurysm following renal transplantation presenting as lumbosacral plexopathy.

A renal transplant patient developed chronic and progressive back and lower extremity pain followed by foot weakness. The correct diagnosis of lumbosacral plexopathy was made after electromyography and nerve conduction studies and the etiology of radiculopathy due to nerve root compression was excluded. This prompted further investigations that led to the discovery of a large internal iliac artery pseudoaneurysm. We emphasize the use of electrodiagnostic studies to investigate patients with back and limb pain for correctly localizing responsible pathology. In this case a potentially lethal situation was correctly identified in a transplant patient.

Aneurysm, False↗

CD28 ligation induces tyrosine phosphorylation of Pyk2 but not Fak in Jurkat T cells.

Protein tyrosine kinases are critical for the function of CD28 in T cells. We examined whether the tyrosine kinases Pyk2 and Fak (members of the focal adhesion kinase family) are involved in CD28 signaling. We found that ligating CD28 in Jurkat T cells rapidly increases the tyrosine phosphorylation of Pyk2 but not of Fak. Paxillin, a substrate for Pyk2 and Fak, was not tyrosine-phosphorylated after CD28 ligation. CD28-induced tyrosine phosphorylation of Pyk2 was markedly reduced in the absence of external Ca2+. Previous studies have shown that the T cell antigen receptor (TCR) induces tyrosine phosphorylation of Pyk2. In this report, the concurrent ligation of CD28 and TCR increased tyrosine phosphorylation of Pyk2; however, the extent of phosphorylation by both receptors was equivalent to the sum of that induced by each receptor alone. The Syk/Zap inhibitor piceatannol blocked CD28, and TCR induced tyrosine phosphorylation of Pyk2, suggesting that Syk/Zap is involved in Pyk2 phosphorylation. In contrast, the phosphatidylinositol 3-kinase inhibitor wortmannin blocked TCR- but not CD28-induced phosphorylation of Pyk2, suggesting that CD28 and TCR activate distinct pathways to induce tyrosine phosphorylation of Pyk2. Notably, depleting phorbol 12-myristate 13-acetate-sensitive protein kinase C did not block CD28- and CD3-induced tyrosine phosphorylation of Pyk2. These data provide evidence for the involvement of Pyk2 in the CD28 signaling cascade and suggest that neither Fak nor paxillin is involved in the signaling pathways of CD28.

CD28 Antigens↗

CD28 ligation induces rapid tyrosine phosphorylation of the linker molecule LAT in the absence of Syk and ZAP-70 tyrosine phosphorylation.

CD28 is a T cell surface molecule that is important for T cell activation. CD28-triggered T cell stimulation involves protein tyrosine phosphorylation, a process that is critical for CD28 function. Recently, a linker molecule has been identified as LAT (Linker for Activation of T cells). Studies involving LAT mutants and reconstitution experiments strongly implicate LAT in playing a critical role in T cell activation. We show in the present report that CD28 ligation induces tyrosine phosphorylation of LAT. CD28-induced tyrosine phosphorylation of LAT was rapid, as it was apparent within 1 min of CD28 ligation, reached a peak by 5 min, and declined thereafter. Previous studies implicated the protein tyrosine kinases ZAP-70 and Syk in the TCR-induced tyrosine phosphorylation of LAT. Here, tyrosine phosphorylation of Syk and ZAP-70 was detected after TCR but not after CD28 ligation. Thus, CD28 ligation appears to induce tyrosine phosphorylation of LAT by mechanisms that are independent of ZAP-70 and Syk. The concurrent ligation of CD28 and TCR increased tyrosine phosphorylation of LAT. These results implicate LAT in CD28 signal transduction pathways and in the co-stimulatory process in T cells.

Adaptor Proteins, Signal Transducing↗

Peripheral vascular disease and renal transplant artery stenosis: a reappraisal of transplant renovascular disease.

BACKGROUND: Renal transplant artery stenosis (RTAS) continues to be a problematic, but potentially correctable, cause of post-transplant hypertension and graft dysfunction. Older transplant recipients, prone to peripheral vascular disease (PVD), may have pseudoRTAS with PVD involving their iliac system. METHODS: We retrospectively analyzed 819 patients who underwent kidney transplantation between 1993 and 1997 to determine the contribution of pseudoRTAS to renal transplant renovascular disease. Univariate analyses were performed for donor and recipient variables, including age, weight, gender, race, renal disease, cholesterol and creatinine values, human leukocyte antigen (HLA) matching, cytomegalovirus (CMV) infection, and immunosuppressive medications. Significant variables were then analyzed by a Cox proportional hazards model. RESULTS: Ninety-two patients (11.2%) underwent renal transplant arteriogram (Agram) or magnetic resonance angiography (MRA) for suspected RTAS. RTAS or pseudoRTAS, defined as one or more hemodynamically significant lesions in the transplant artery or iliac system, was evident in 44 patients (5.4%). Variables significantly associated with RTAS by univariate analysis were weight at the time of transplant (p = 0.0258), male gender (p = 0.034), discharge serum creatinine > 2 mg/dL (p = 0.0041), and donor age (p = 0.0062). Variables significantly associated with pseudoRTAS by univariate analysis were weight at the time of transplant (p = 0.0285), recipient age (p = 0.0049), insulin-dependent diabetes mellitus (IDDM; p = 0.0042), panel reactive antibody (PRA) at transplant (p = 0.018), and body mass index (p = 0.04). Weight at transplant and donor age remained significantly associated with an increased risk for RTAS in a multivariate stepwise Cox proportional hazards model. IDDM, transplant PRA, weight at transplant, and donor age were significantly associated with an increased risk for pseudoRTAS in a multivariate stepwise Cox proportional hazards model. Importantly, both RTAS and pseudoRTAS were associated with poorer graft survival (p < 0.007 for each). CONCLUSIONS: Renal transplant renovascular disease encompasses pre-existing PVD acting as pseudoRTAS, as well as classical RTAS. Efforts to identify and correct renal transplant renovascular disease of either nature are important, given its negative impact on graft survival.

Adult↗

Treatment with humanized monoclonal antibody against CD154 prevents acute renal allograft rejection in nonhuman primates.

CD154 is the ligand for the receptor CD40. This ligand-receptor pair mediates endothelial and antigen-presenting cell activation, and facilitates the interaction of these cells with T cells and platelets. We demonstrate here that administration of a CD154-specific monoclonal antibody (hu5C8) allows for renal allotransplantation in outbred, MHC-mismatched rhesus monkeys without acute rejection. The effect persisted for more than 10 months after therapy termination, and no additional drug was required to achieve extended graft survival. Indeed, the use of tacrolimus or chronic steroids seemed to antagonize the anti-rejection effect. Monkeys treated with antibody against CD154 remained healthy during and after therapy. The mechanism of action does not require global depletion of T or B cells. Long-term survivors lost their mixed lymphocyte reactivity in a donor-specific manner, but still formed donor-specific antibody and generated T cells that infiltrated the grafted organ without any obvious effect on graft function. Thus, therapy with antibody against CD154 is a promising agent for clinical use in human allotransplantation.

Animals↗

Surgical portosystemic shunts for treatment of portal hypertensive bleeding: outcome and effect on liver function.

BACKGROUND: Since the advent of liver transplantation and transjugular intrahepatic portosystemic shunts (TIPS), the role of surgical portosystemic shunts in the treatment of portal hypertension has changed. However, we have continued to use portosystemic shunts in patients with noncirrhotic portal hypertension and in patients with Child's A cirrhosis. METHODS: We performed 48 surgical portosystemic shunt procedures between 1988 and 1998. The outcomes of these patients were evaluated to assess the efficacy of this treatment. Data from 39 of 48 patients were available for analysis. The average follow-up was 42 months. RESULTS: Liver function generally remained stable for the patients; only 2 patients had progressive liver failure and required transplant procedures. Gastrointestinal bleeding (3 patients), encephalopathy (3 patients), and shunt thrombosis (3 patients) were rare. Patient survival was 81% at 4 years, similar to survival with liver transplantation (P = .22). CONCLUSIONS: Surgical shunts remain the treatment of choice for prevention of recurrent variceal bleeding in patients with good liver function and portal hypertension.

Ammonia↗

Disseminated aspergillosis involving the brain: distribution and imaging characteristics.

BACKGROUND AND PURPOSE: Systemic invasive aspergillosis involves the brain through hematogenous dissemination. A retrospective review of 18 patients with aspergillosis involving the brain was performed in order to present imaging findings and thereby broaden the understanding of the distribution and imaging characteristics of brain Aspergillus infection and to facilitate its early diagnosis. METHODS: The neuroimaging studies of 17 biopsy- or autopsy-proved cases and one clinically diagnosed case were examined retrospectively by two neuroradiologists. The studies were evaluated for anatomic distribution of lesions, signal characteristics of lesions, enhancement, hemorrhage, and progression on serial studies (when performed). Medical records, biopsy reports, and autopsy findings were reviewed. RESULTS: Thirteen of 18 patients had involvement of the basal nuclei and/or thalami. Nine of the 10 patients with lesions at the corticomedullary junction also had lesions in the basal nuclei or thalami. Callosal lesions were seen in seven patients. Progression of lesion number and size was seen in all 11 patients in whom serial studies had been performed. Enhancement was minimal or absent in most cases. There was gross hemorrhage in eight of the 18, and definite ring-enhancement in three. CONCLUSION: Among our cases, lesions in perforating artery territories were more common than those at the corticomedullary junction. Ring enhancement and gross hemorrhage may be present, but are not necessary for the prospective diagnosis.

Adult↗

Current management of esophageal variceal bleeding.

Recent trends in the clinical management of bleeding esophageal varices include a shift away from endoscopic variceal sclerotherapy toward endoscopic variceal ligation. The excellent efficacy of the latter and its lower complication rate favor its increased use. Similarly, the minimally invasive nature of the TIPS procedure and its successful implementation by invasive radiologists have further reduced the need for surgical shunts in general, as well as when endoscopic intervention has failed. A multidisciplinary approach toward evaluation and treatment of variceal hemorrhage can be expected to improve the outcomes of these patients. More selective application of each of the therapies, either alone or in combination with other modalities, leads to improved results, as recently demonstrated by a series comparing outcomes of surgical shunts when used alone or as a preface to liver transplantation.

Endoscopy↗

Pancreas transplantation at the University of Wisconsin.

Based on the University of Wisconsin experience with 653 cadaver pancreas transplant performed since 1985, we noted that: 1. The overall 5- and 10-year patient survival rates were 87% and 80%, respectively. The 5- and 10-year pancreas graft survival rates were 70% and 60%, respectively, and the 5- and 10-year kidney graft survival rates were 80% and 60%, respectively. 2. An immunosuppressive regimen including TAC and MMF in both solitary pancreas and SPK transplants was very effective in reducing the rate of acute rejection and improving graft survival. 3. Pancreas graft survival in recipients of solitary pancreas transplants was equivalent to that in SPK recipients in the TAC-MMF era. 4. Anti-IL2 receptor monoclonal antibodies were safe and effective in solitary pancreas and SPK transplants. 5. Excellent short-term graft survival can be achieved in solitary pancreas transplants using enteric drainage.

Adolescent↗

Posttransplant infection in enteric versus bladder-drained simultaneous pancreas-kidney transplant recipients.

BACKGROUND: Although bladder drainage of the pancreas remains the most common site for drainage of exocrine secretions, enteric drainage is becoming more common in the United States. The most common cause of morbidity after pancreas transplantation is infection, particularly recurrent urinary tract infection. METHODS: We examined the incidence of infectious complications for enteric-drained (ED) versus bladder-drained (BD) simultaneous pancreas-kidney transplants (PTx) to determine the incidence of post-transplant infection. The patient cohort included simultaneous pancreas-kidney PTx recipients from June 1995 through August 1997 using a similar induction protocol with antithymocyte globulin, mycophenolate mofetil, prednisone, and Neoral. During this time period, 48 BD PTx and 78 ED PTx were performed. Demographic data including age of transplant, gender, race, and duration of initial hospital stay were similar. However, mean follow-up for the BD PTx was 1.9 years vs. 0.9 years for ED PTx. Rejection, infection, and graft and patient survival rates were estimated by the method of Kaplan and Meier. RESULTS: For the entire cohort, 1-year patient survival was 98%, kidney survival 94%, and pancreas survival 93%. There was no difference in survival between ED or BD PTx. At 6 months, kidney transplant rejection had occurred in 38% of BD PTx vs. 30% of ED PTx. Steroid resistant rejection was similar (BD 19%, ED 17%). Postoperative pancreatic leak occurred in 12% BD PTx and 5% ED PTx (P=0.06). There was no significant difference in time to first infection or first abdominal infection between groups. Opportunistic infections were much less likely to occur in ED recipients by 1 year (12% vs. 31%, P=0.002). Both cytomegalovirus infection rates (BD 21% vs. ED 8%, P=0.04) and fungal infection rates (BD 17% vs. ED 4%, P=0.04) were lower in ED PTx. The rate of first urinary tract infection was dramatically decreased with ED. At 1 year, only 20% of ED PTx developed a urinary tract infection vs. 63% of BD PTx (P=0.0001). CONCLUSION: Enteric drainage of the pancreas is more physiologic, has similar results to bladder drainage, but has less infectious complications, particularly urinary tract infections.

Adult↗

A study comparing mycophenolate mofetil to azathioprine in simultaneous pancreas-kidney transplantation.

BACKGROUND: Mycophenolate mofetil (MMF; Cell-Cept) is a potent and selective inhibitor of B and T lymphocyte proliferation that has proven effective in reducing the incidence of acute rejection in cadaveric kidney transplant recipients in several randomized, blinded clinical studies. Because the frequency and characteristics of rejection episodes may be different and more severe after combined pancreas-kidney transplantation, we hypothesized that MMF would have a significant impact on pancreas-kidney rejection and graft outcome. Therefore, we compared the efficacy of MMF versus azathioprine (AZA) in cyclosporine-treated simultaneous pancreas-kidney transplantations. METHODS: A retrospective comparison of 358 consecutive primary SPK transplantations performed from 1990 to 1997 was conducted. Patients received either MMF (n=109, 3 g/day) or AZA (n=249, 2 mg/kg q.d.) in combination with cyclosporine-based immunosuppression. All patients received a quadruple-drug sequential induction protocol with either OKT3 or Atgam. Several outcome parameters, including patient and graft survival rates and frequency of rejection, were analyzed. RESULTS: MMF-treated patients demonstrated a markedly reduced rate of biopsy-proven kidney rejection (31 vs. 75% AZA, P=0.0001), clinically significant pancreas rejection (7 vs. 24% AZA; P=0.003), and steroid-refractory rejection (15 vs. 52% AZA; P=0.01). As a result, kidney and pancreas allograft survival was significantly better in MMF patients compared with AZA patients (2-year survival rates: kidney, 95 vs. 86%; and pancreas, 95 vs. 83%). Although surgical infections after transplantation were more frequent in MMF patients, MMF patients were more likely to have undergone enteric drainage. Importantly, we did not observe an increased incidence of any of the bacterial, fungal, or viral infections that typically plague immunosuppressed transplant recipients. CONCLUSIONS: This retrospective study demonstrates that MMF is a highly effective immunosuppressant in SPK transplantation. It is not associated with an increased risk of opportunistic infections when a balanced immunosuppressive management approach is used. MMF strikingly reduces the frequency of acute cellular and steroid-resistant rejection. As a result of this combined experience, it is not unexpected then that we observe significantly improved graft survival rates in MMF-treated SPK patients compared with patients receiving a more traditional immunosuppressive regimen.

Acute Disease↗

Liver transplantation as definitive therapy for complications after arterial embolization for hepatic manifestations of hereditary hemorrhagic telangiectasia.

Experience with hepatic artery embolization for the treatment of symptomatic hepatic arteriovenous malformations (AVMs) in Rendu-Osler-Weber disease is limited. We report 2 cases of hepatic AVMs that caused mesenteric angina-like symptoms that were treated with embolization. Both patients developed parenchymal and bile duct necrosis, intrahepatic bilomas, and refractory biliary sepsis, subsequently leading to liver failure. We hypothesize that the pathophysiological cause of biliary necrosis in this setting is similar to that which occurs in the setting of hepatic artery thrombosis of the liver allograft. Progressive liver failure in these patients was treated successfully by liver transplantation. Liver transplantation offers definitive therapy by removing the source of ongoing sepsis, restoring normal liver function, and eliminating the intrahepatic AV shunt.

Embolization, Therapeutic↗

Infant pediatric liver transplantation results equal those for older pediatric patients.

METHODS: From July 1984 to July 1995, 99 pediatric patients underwent 127 orthotopic liver transplants (OLT) at the University of Wisconsin Children's Hospital. The patients were divided into four groups according to age at time of transplant: group I, 0 to 6 months (n = 20); group II, 6 to 12 months (n = 18); group III, 1 to 2 years (n = 10); and group IV, 2 to 18 years (n = 51). A retrospective analysis was performed to compare these four groups with regard to preoperative indications and demographics, intraoperative technique, complications, and survival. All patients were followed up for 2 to 13 years. RESULTS: Biliary atresia was the most common indication for OLT in all four groups. The average waiting period varied from 19+/-18 days for group I to 44+/-64 days for group IV. Reduced-size liver transplant (I, 41%; II, 52%; III, 28%; IV, 21%), split-liver transplant (I, 0%; II, 7.4%; III, 17%; IV, 2.9%), or whole-liver transplant techniques were used. Although postoperative Intensive Care Unit stay was longer for the 0- to 6-month-old patients (I, 20+/-64; II, 7.6+/-9; III, 13+/-17; IV, 6.8+/-14 days), the total hospital stay (I, 43+/-63; II, 33+/-34; III, 32+/-20; IV, 29+/-31 days) was similar for all patients. The incidence of hepatic artery thrombosis (I, 19%; II, 19%; III, 27%; IV, 16%), biliary tract complications (I, 4.8%; II, 15%; III, 20%; IV, 14%), and retransplantation (I, 9.5%; II, 41%; III, 33%; IV, 14%) were not significantly different between the four groups. Portal vein thrombosis (I, 9.5%; II, 11%; III, 6.6; IV, 0%) and primary nonfunction (I, 9.5%; II, 7.4%; III, 0%; IV, 3.1%) occurred more frequently in the 0- to 6-month and 6- to 12-month groups, however, the 1-, 5-, and 10-year survival rate for patients (I, 85%, 79%, 79%; II, 89%, 74%, 74%; III, 80%, 80%, 80%; IV, 84%, 75%, 75%, respectively) and primary liver allografts (I, 69%, 69%, 69%; II, 72%, 72%, 63%; III, 70%, 70%, 70%; IV, 71%, 57%, 57%, respectively) were not significantly different (P = .98 and P = .83). CONCLUSION: These results demonstrate that OLT can be effectively performed on infants of all ages and that OLT should not be delayed because of age.

Adolescent↗