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Cystic renal dysplasia, or polycystic kidney disease, may be of no aeromedical significance if it is
unilateral and the other kidney is functional. Bilateral disease will nearly always be identified early in
childhood, as commonly seen in autosomal recessive (“juvenile” or “infant”) polycystic kidney disease.
Adult polycystic kidney disease (APKD), on the other hand, often leads to severe renal dysfunction. It is
an autosomally dominant acquired condition that commonly presents in later life. Its incidence ranges
from 1 in 350 to 1 in 1000 individuals. APKD accounts for 5 to 15 percent of patients with renal failure
requiring transplantation or dialysis. It presents in individuals from the second through the ninth decade
of life.
It is important that patients with polycystic disease undergo radiographic imaging to rule out abdominal
aortic or cerebral aneurisms, including those of the circle of Willis6. Other associated anomalies include
hepatic, pancreatic, splenic, and pulmonary cysts as well as colonic diverticula, and mitral valve prolapse.
6 Circle of Willis: cerebral arterial circle. After Thomas Willis, English physician (1621-1675)
ICAO Preliminary Unedited Version — November 2009 III-6-11
Aside from renal cysts, other common congenital defects include unilateral anomalies, malposition of the
kidneys, and duplication of the collecting system. Renal hypoplasia is defined as an absent or adult
kidney that weighs less than 50 g. The other kidney may compensate so well by physiologic hypertrophy
that the condition is undetectable except by radiographic imaging.
Horseshoe kidney is a pelvic kidney with an inferior isthmus conjoining the two poles of the two renal
units. This isthmus prevents normal renal ascent during development at the point of the inferior
mesenteric artery. Complications of this congenital anomaly may include infection, stone disease and,
later, arterial hypertension. Once the condition is identified, some references recommend routine
screening for these complications.
Malposition of a kidney, such as a pelvic location, occurs in about one in 900 people. Complications may
include kinking of ureters, obstruction of urinary flow, hypertension, and pain. If there are no
complications and the patient is asymptomatic with normal function of the kidney, the condition has little
aeromedical significance.
Duplication of the collecting system occurs in about three per cent of the population. In most cases it has
no aeromedical significance, but occasionally it may be associated with obstruction and stasis of urine. In
these instances, it may cause stone disease and recurrent infection.
Clinical features
Adult polycystic kidney disease (APKD) most commonly presents in the fourth to sixth decades with
haematuria, flank pain, gastrointestinal symptoms, renal colic, and/or hypertension. Anaemia or elevated
serum creatinine may also be found during initial presentation. Up to 40 percent of APKD patients also
have berry aneurisms, with nearly nine per cent of these patients dying from rupture and subsequent
subarachnoid haemorrhage. Intracerebral arterial haemorrhage may be a presenting sign for this disease,
secondary to the hypertension seen in this population.
Autosomal recessive polycystic kidney disease, conversely, results in death of nearly 50 per cent of all
newborns with this condition within the first few hours or days of life. Of the infants that survive,
approximately 50 per cent are alive at age 10, and some of those are completely asymptomatic throughout
their lives. Obviously, the natural history of this disease makes it a rare diagnosis for the aeromedical
examiner.
Medullary sponge kidney commonly presents as renal colic, followed by a urinary tract infection, then
gross or microscopic haematuria. One third to one-half of all patients with medullary sponge kidney
eventually develops urinary stone disease, and it is often an IVU that leads to the diagnosis. The other
congenital anomalies mentioned are usually radiographically identified after clinical presentation of
nephroureteral stone disease, haematuria, infection, hypertension, abdominal mass, or other symptoms.
Diagnosis
Sonography is one of the mainstays of diagnosing and differentiating renal cystic disease from other
anomalies. Using ultrasound, a common simple cyst reveals the absence of internal echoes, a sharply
defined wall, good sound transmission through the cyst with acoustic enhancement behind the cyst, and a
spherical or ovoid shape. Lack of the characteristics warrants further investigation, such as contrast
enhanced CT or MRI, to rule out malignancy or other entities. APKD is classically bilateral and is
characterized by a confluence of multiple large renal cysts on ultrasound images. Cysts may be found by
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Manual of Civil Aviation Medicine 1(155)
