Andersons pediatric cardiology 1616

blood pressure should be monitored throughout the procedure Newer techniques include magnetic resonance angiography314,315 and computed tomographic and spiral angiography.283 These have the advantage of being less invasive, and can normally be performed without general anesthesia in older children and adolescents, although as yet they are not accurate enough to replace the gold standard of formal digital subtraction arteriography.309 Interventional treatments of renovascular hypertension include percutaneous transluminal angioplasty (see Fig 60.4) and open surgery In general, angioplasty is the preferred approach for discrete nonostial stenoses, while open surgery is often needed for ostia, multiple and extensive stenoses.316,317 The rate of cure for surgery in renovascular hypertension in children is high.194,309,317,318 It varied between 85% and 100% in various series of properly selected patients, with no operative deaths in one large series.318 The operative techniques vary according to the nature of the disease They include renal arterial reconstruction and reimplantation, autotransplantation of the kidney, and venous grafting or prosthetic bypass of the stenosis.283,317,318 Decisions regarding treatment where there is abdominal aortic narrowing associated with renal artery stenosis are challenging because surgical correction of the renal arterial stenosis by vascular shunts from above the coarctation may compromise flow to other organs Successful outcomes have been reported in the majority of children undergoing surgery for renovascular hypertension associated with abdominal aortic narrowing.285,318 Percutaneous transluminal angioplasty is the preferred approach for discrete nonostial stenoses The technique is less successful with ostial stenosis, the presence of intrarenal stenoses and abnormalities in other vascular beds, or the long segment renal arterial stenosis often seen in neurofibromatosis type 1 Several published series show an overall favorable outcome, including a number of cases with neurofibromatosis type 1.281,291,319–324 Restenosis is relatively common, occurring in up to one-quarter of cases, and is commoner if a stent has been placed in the vessel There is relatively little experience of stenting stenosed arteries in children.317,324,325 Stenosis may develop in the previously normal renal artery on the unaffected side.326 The progressive nature of fibromuscular dysplasia in children suggests that every attempt should be made to preserve renal function Nephrectomy should be performed only if the kidney is small or scarred and has very poor function, accounting for less than 20% of total function Renal Parenchymal Disease The renal disease causing hypertension is usually evident from the initial clinical and laboratory evaluation (see Boxes 60.1 and 60.2) Chronic pyelonephritis with renal scarring is a major cause of childhood hypertension.208,327,328 Some tertiary centers have reported the development of hypertension in up to 25% of patients with severe reflux nephropathy, although other centers have reported a much lower prevalence.328 A careful search for renal scarring must always be performed using scintigraphic techniques, since renal ultrasound used in isolation may fail to identify renal scarring.329 If scarring is demonstrated, a contrast micturating cystourethrogram, or indirect radioisotope cystogram, should be considered Treatment of hypertension is usually medical, as the damage is often bilateral and affects more than one segment of the kidney Where investigations indicate that the cause of hypertension is a small, scarred, and poorly functioning kidney, with a normal unscarred kidney on the other side, removal of the damaged kidney may cure the hypertension and remove the need for antihypertensive therapy Occasionally, partial nephrectomy may be indicated for focal scarring where the remainder of the kidney is undamaged; in these cases, sampling of renin in the renal vein is usually required to confirm isolated hyperreninemia arising from the scarred segment Obstruction at the pelviureteric junction is occasionally associated with hypertension, which can be cured in some instances by a pyeloplasty.330 Hypertension is common in acute nephritic syndrome Indeed, this diagnosis has to be considered in any child with unexplained acute hypertension Plasma renin, at least to commence with, is low because of the retention of sodium.331,332 Hypertension is also common in chronic glomerulonephritis (see Box 60.1), and is almost invariable when renal function declines Diseases associated with widespread arteriolar damage, such as hemolytic uremic syndrome, systemic lupus erythematosus, and polyarteritis nodosa, are often accompanied by hypertension Polycystic kidneys are an important cause of hypertension The raised pressures are seen early in the autosomal recessive form of the condition encountered in childhood.333 Hypertension may also develop in childhood in the more common autosomal dominant variant.334,335 Hypertension is less common with primary interstitial tubular diseases, such as the Fanconi syndrome or juvenile nephronophthisis, and with the diseases associated with salt wasting, such as renal dysplasia or obstructive uropathy in infancy When renal insufficiency supervenes, however, even children with these conditions may develop hypertension Primary Hyper-Reninism Severe hypertension is uncommon in children with nephroblastoma, also known as Wilms tumor It can occur when renal ischemia is present, or after hemorrhage into the tumor Occasionally, production of renin by the tumor has been described.336 Tumors of the juxtaglomerular cells, or hemangiopericytomas, are extremely rare With these tumors, the activity of renin is elevated in the plasma, and there is often evidence of secondary hyperaldosteronism The tumors are single, benign, and small, measuring from 0.8 to 4 cm.194 They should be suspected when a raised level of renin is found in the renal vein in association with cross-cutting imaging of the kidney such as a CT or MRI of the kidney.337 They may be apparent as a translucent area seen during the nephrographic phase of a selective renal arteriogram.338 Surgical removal of the tumor is indicated Aortic Coarctation Aortic coarctation is one of the most important causes, after renal disease, of severe hypertension in children.339 The cause of the hypertension in patients with coarctation is complex and not fully explained The main hypotheses include mechanical obstruction,340 the neural theory of altered autonomic and baroreceptor function,341–343 and activation of the renin-angiotensin system.344,345 Despite apparently successful surgical correction of the aortic narrowing, ongoing or recurrent hypertension is well recognized and common, and often observed even in patients with a successful repair with minimal or no residual gradient demonstrable in the aortic arch.346,347 It may be considered a long-term condition even after surgical correction.346 The etiology of this hypertension is thought to be multifactorial In a recent review, this was discussed in detail, and the authors concluded that the current data support the presence of a complex interdependent relationship of hypertension and vascular dysfunction following coarctation of aorta repair with arterial stiffness predominantly increased in precoarctation site arteries and not in the postcoarctation arteries.339 The diagnosis and treatment of aortic coarctation is discussed at length in Chapter 46