Page 710 - Hematology_ Basic Principles and Practice ( PDFDrive )

602 Part V Red Blood Cells

renal function (see also organ-specific complications, kidney in Clini- the vasa recta caused by sickling (Fig. 42.13). When water deprived,
cal Presentation and Management, later). these patients cannot maximally concentrate their urine and develop
Other risk factors for the development of chronic renal failure hypovolemia and dehydration.
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include use of NSAIDs and a genetic predisposition associated with Other abnormalities of renal tubular dysfunction found in sickle
the CAR β-globin haplotype; the latter has been suggested as an cell anemia include an incomplete form of distal renal tubular acidosis
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indication for BMT to prevent this outcome. Acute renal failure with hyperchloremic metabolic acidosis and hyperkalemia. The
from infarction may result from hypovolemia, sepsis, hepatorenal hyperkalemia may respond to oral sodium bicarbonate.
syndrome, cardiac failure, renal vein thrombosis, and rhabdomyolysis.
These patients typically survive and recover their renal function with Urinary Tract Infections
no increased risk of developing chronic renal failure. Urinary tract infections and pyelonephritis are discussed under infec-
There are seven well-described nephropathies that affect patients tious complications.
with either sickle cell trait or disease. These are gross hematuria,
papillary necrosis, nephrotic syndrome, renal infarction, inability Renal Medullary Carcinoma
to concentrate urine, pyelonephritis, and renal medullary Sickle cell trait has been reported to be associated with renal medul-
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carcinoma. 206 lary carcinoma. Presentation is with gross hematuria, abdominal or
Renal transplantation is recommended for patients with sickle cell flank pain, or significant weight loss. The disease may be metastatic
and end-stage renal diseases. at diagnosis, and the prognosis is poor. There is a weak association
of renal medullary carcinoma with Hb SC disease but no identified
Renal Endocrine (Erythropoietin) Deficiency association with sickle cell anemia. The reason for these patterns of
This is discussed under Basic Management and Disease disease is unknown.
Modification.

Gross Hematuria Priapism
Hematuria may result from microthrombi formation in the peritu-
bular capillaries of the renal medulla or from frank papillary necrosis. Priapism is a condition that is characterized by a sustained erection
Significant hematuria may resolve with high urinary flow through that does not result from sexual desire and is not relieved by sexual
oral hydration and bed rest. Hematuria that lasts longer than 1–2 activity. Stuttering priapism is a separate entity that is character-
weeks or the need for transfusion may require maintenance of a high ized by multiple, brief episodes of sustained unwanted erection. It
urinary flow using a combination of hypotonic fluids and loop diuret- has been reported to affect 6.4% to 42% of boys and men with
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ics and urinary alkalinization using sodium bicarbonate and acetazol- SCD and can also occur in sickle cell trait. Its peak frequencies
amide. These therapies are aimed at changing the acidic, hypertonic are between ages 5 and 13 years and 21 and 29 years. Priapism is
environment of the renal medulla that favors erythrocyte dehydra- most likely to develop in patients with lower Hb F levels and reticu-
tion, increased Hb S concentrations, and Hb S polymerization. If locyte counts, increased platelet counts, and the Hb SS genotype.
bleeding persists for 72 hours despite these measures, then alternative Priapism caused by SCD is usually ischemic, or low-flow, priapism.
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treatment should be considered. These may include oral urea, (High-flow priapism is caused by unregulated arterial flow and can
ε-aminocaproic acid, and vasopressin. Embolization or nephrectomy be distinguished from low-flow priapism by a blood gas obtained
should be reserved for prolonged, life-threatening cases of hematuria from the corpora.) Most likely, priapism begins with a physiologic
that require multiple transfusions. erection. The relative stasis of blood within the corpora leads to a
Increased hematuria can also be seen as a consequence of delayed decrease in oxygen tension and development of acidosis, predisposing
hemolytic transfusion reactions (discussed in Exacerbations of to Hb S polymerization in the corporal sinusoids, venous occlu-
Anemia). sion, and low-flow priapism. Pain develops as the corpora become
increasingly ischemic after approximately 4 hours of erection. In
Papillary Necrosis a minority of patients, usually postpubertal, the engorgement also
Papillary necrosis is most often detected incidentally by imaging or affects the corpus spongiosum and glans. The mild acidosis that
microscopic examination of urine in asymptomatic patients. Sloughed accompanies hypoventilation during sleep may also contribute to the
papilla may cause ureteral obstruction and urinary tract infection. In pathophysiology. Impotence is the primary complication of priapism,
addition to broad-spectrum antibiotics, this occurrence requires although some patients with a history of multiple episodes of pria-
emergent relief of the obstruction with a retrograde ureteral stent or pism and significant corporeal fibrosis may report adequate erections
placement of a percutaneous nephrostomy tube. NSAIDs should be and maintain active sex lives. Corporeal ischemia during priapism
avoided in patients with papillary necrosis. Otherwise treatment is as may induce local inflammation, causing the fibrosis responsible for
for hematuria. impotence.
The goal of treatment is to relieve priapism and maintain
Proteinuria potency. Patients should be educated to seek medical attention for
Proteinuria has been found in 20% to 30% of patients with SCD. unrelenting erection of more than 2 hours’ duration. Detumescence
Increasing age and low Hb levels correlate with proteinuria. Protein- within 12 hours is optimal to retain potency. After 72 hours,
uria can progress to nephrotic syndrome characterized by proteinuria, impotence is more likely. The strategy is prompt initiation of sup-
hypoalbuminemia, edema, and hyperlipidemia. Angiotensin- portive medical therapy with intravenous hydration and analgesia
converting enzyme (ACE) inhibitors produce a significant reduction and involvement by a urology consultant if the priapism persists for
in sickle proteinuria, although it is unclear if ACE inhibitors might more than 4 hours; aspiration of blood from the corpora with or
slow or halt the progression of proteinuria to nephrotic syndrome without irrigation, and injection of an α-adrenergic agonist should
and renal failure. 211,212 Angiotensin II inhibitors are being studied for be considered (Guidelines of the American Urological Association,
a potential role in decreasing sickle cell–related proteinuria and renal https://www.auanet.org/education/guidelines/priapism.cfm). If pria-
function deterioration. pism persists 12 hours, options include partial-exchange transfusion
to reduce the Hb S level to less than 30% with a total Hb of less than
Hyposthenuria and Other Abnormalities of 10 g/dL or irrigation as outlined earlier. The latter procedure is less
Tubular Function effective after 36 hours of priapism. Irrigation should be performed
The inability to maximally concentrate urine (hyposthenuria) in using penile anesthesia (dorsal nerve block; circumferential penile
response to water deprivation is an early finding of sickle cell block; or subcutaneous, local, penile shaft block). All irrigation in
nephropathy. Both sickle cell trait and SCD patients may be affected. boys should be performed under conscious sedation. There is anec-
Hyposthenuria is the cumulative result of recurrent microinfarcts in dotal evidence for the use of hydralazine to treat acute priapism. 216