Page 19 - Journal of Special Operations Medicine - Winter 2016

(MR) imaging. If there are no pathologic sequelae from subsequent normalization of EPO levels after nephrec-
the cysts, neoplasm is ruled out, and an asymmetric tomy. In a case of URCD, erythrocytosis resolved after
presentation of ADPKD is not likely, conservative man- cystectomy; however, EPO levels were not documented.
24
agement may be followed because the disease is non- In contrasting, there are cases of renal cysts associated
progressive. 3,11 The differential diagnosis for URCD with elevated serum EPO and persistent erythrocytosis
includes multiple simple cysts (MSCs), which may also despite treatment of the renal cyst in a child as well as
21
be unilateral. Currently, it is believed that URCD and in a patient with confounding primary PV. 20
MSCs may represent the same disease along a contin-
uum of increasing cyst quantity. 12 The cause for the disparity among cases of EPO levels,
erythrocytosis, and renal cyst is not completely under-
This case is unique in the association of URCD with stood. It is postulated that renal cysts may be a nidus
headache, hypertension (HTN), and erythrocytosis. for irritation on EPO-producing cells in the kidney or
24
Erythrocytosis (the term is often used interchangeably that the cyst may compress renal vasculature, leading to
with polycythemia) is defined as an increase in hema- local renal hypoxemia and, ultimately, increased EPO
tocrit of greater than 52% in men and 48% in women. production. It is also shown the EPO is sometimes el-
25
The cause of erythrocytosis may be relative, with a evated in the cyst fluid itself, leading to speculation that
mildly elevated hematocrit in the setting of stable red the cyst may serve as a reservoir for EPO. The normal
26
blood cell mass and contracted plasma volume, or ab- EPO levels reported in this case are inconsistent with
solute, with an increase in circulating red cell mass. some reports in the literature 20–22,26 ; however, EPO levels
Absolute polycythemias can be further categorized into are not always reported in similar cases because it is not
primary or secondary polycythemias. Primary polycy- the standard of practice in some departments. Further-
24
themia is largely a problem of hematopoietic progenitor more, serum EPO levels are variable and depend on tim-
cells. Secondary polycythemias are diverse and caused ing of sampling. If EPO levels are produced in response
by conditions such as hypoxia that increase production to local renal hypoxemia that may be exacerbated by
of the hematopoietic growth factor EPO. 13 hyperviscosity syndrome, and management was initi-
ated with phlebotomy, the EPO levels may normalize
When approaching a patient with erythrocytosis, the at the time of sampling, as in our case. Or, it is possible
diagnostic decision tree includes ruling out causes for that the EPO levels were initially elevated in our patient;
secondary erythrocytosis. If secondary erythrocytosis is however, upon the time of sampling, the EPO produc-
unlikely, an assay for JAK2 mutation, as well as measure- tion had reached a plateau and started to decrease. In
ment of serum EPO levels, may be indicated . The cur- an animal study of experimental hydronephrosis, it was
14
rent World Health Organization criteria for the diagnosis proposed that during early stages of hydronephrosis,
of PV require the presence of two major criteria, an addi- the renal cells produce EPO that correlates with eryth-
tional major, or an additional minor criteria; these include rocytosis; however, during later stages, pressure atrophy
clonal genetic abnormalities and serum EPO levels. 15,16 occurs and EPO production falls, correlating with re-
solving erythrocytosis. 25
EPO is produced by the peritubular cells of the kidney in
response to hypoxemia. In cases of primary erythrocyto- In addition to erythrocytosis, the patient in this case also
sis, EPO levels will be appropriately low or normal. In presented with new-onset HTN and headache. The as-
15
cases of secondary erythrocytosis, EPO levels may range sociation of simple renal cysts, 27–29 giant renal cysts,
23
from normal to elevated. In a study of 116 patients with and URCD with arterial HTN is well documented in
6
PV, it was reported that low EPO levels correlated with the literature. Furthermore, treatment of the renal cysts
PV and provided a 97% specificity. In this same study, results in a significant reduction of HTN. An associa-
17
6
96.8% of patients with secondary or idiopathic erythro- tion is proposed between the size of the cyst and HTN.
27
cytosis had normal or high EPO levels (i.e., greater than The pathogenesis of HTN from renal cysts may result
3.3IU/L). As in this case, EPO levels were measured in from three physiologic conditions: renal cysts stimulat-
17
the normal range, which, when combined with a nega- ing direct renin release, loss of nephrons causing HTN,
tive JAK2 mutation, helped to exclude PV as a potential or cysts compressing renal vasculature that would stim-
cause for the patient’s erythrocytosis. ulate an increase renin activity. It is also proposed that
28
erythrocytosis itself may be an indirect and potent stim-
In cystic renal disease, the increase in EPO levels in renal ulant of HTN. 30
cyst walls, renal cyst fluid, and serum is inconsistently
demonstrated. 18–23 Markedly elevated serum EPO levels Hyperviscosity syndrome occurs when abnormalities in
are reported in ADPKD. Elevated serum EPO levels the cellular component of the blood, including eryth-
18
are reported in cases of a giant renal cyst with erythro- rocytosis, or in the protein component of the blood
cytosis 22,23 and renal cysts without erythrocytosis with lead to increased blood viscosity, impaired blood flow,
19

Unilateral Renal Cystic Disease: Case Report 3