Clinical Practice Guideline

for

CHRONIC KIDNEY DISEASE

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: Chronic kidney disease (CKD) is a worldwide public health problem and in the US, the incidence and prevalence of kidney failure are rising as evidenced by the age-, sex-, and race-adjusted incidence of end-stage renal disease increasing by 43% during the decade following 1991.  The major outcomes of CKD, regardless of the underlying etiology, include progression to kidney failure, complications associated with decreased kidney function, and cardiovascular disease (CVD).  Approximately 19 million Americans older than age 20 have CKD, and an additional 435,000 have end-stage renal disease.  CKD is 100 times more prevalent then end-stage renal disease, and its incidence in increasing at an even faster rate.  The financial burden of end-stage renal disease is substantial, with an estimate of nearly $23 billion in annual direct medical costs in the US.

 

CKD is defined as a glomerular filtration rate (GFR) <60 mL/min/1.73 m2 of body surface area for > 3 months.  An alternate disease definition is the presence of kidney damage or decreased level of kidney function for three months or more, irrespective of diagnosis.  In the US, the major causes of CKD are diabetes, hypertension, glomerulonephritis, and tubulointerstitial disease.  Most patients are totally asymptomatic until later in the disease process.  Symptoms and/or signs of renal failure would include weakness, anemia (from chronic disease), easy fatigability (from the anemia), anorexia, vomiting, mental status changes or seizures, and edema.  There is also a strong associated between frailty and CKD in the general US population, and is particularly strong among persons with a GFR <45 mL/min/1.73 m2.  Frailty is also independently associated with mortality.

 

Earlier stages of chronic kidney disease can be detected through laboratory testing.  Treatment of these early stages of chronic kidney disease is effective in slowing the progression toward kidney failure.  Unfortunately, chronic kidney disease is ‘‘under-diagnosed’’ and ‘‘under-treated’’ in the United States, resulting in lost opportunities for prevention.  One reason is the lack of agreement on a definition and classification of stages in the progression of chronic kidney disease, as well as the best target group of patients to screen.  Measurement of serum creatinine and estimation of GFR can identify patients with reduced kidney function.  Measurement of urinary albumin excretion can identify some, but not all, patients with kidney damage.  Screening asymptomatic individuals at increased risk could allow earlier detection of chronic kidney disease.  High-risk groups that should be screened for CKD include patients who have a family history of the disease and patients with diabetes, hypertension, recurrent urinary tract infections, urinary obstruction or any systemic illness that affects the kidneys.  Of those at high risk, diabetes is the most common cause of CKD.

 

In most cases, the GFR estimate (eGFR) is calculated from the measured serum creatinine level after adjustments for age, sex and race.  A GFR of 100 mL/min/1.73 m2 is considered normal for women and 120 mL/min/1.73 m2 is normal for men.  There are two commonly used formulas for estimating the GFR; the Modification of Diet in Renal Disease (MDRD) study equation or the Cockroft-Gault equation.  The MDRD equation is considered by most to be more accurate, but has been found to underestimate the GFR in healthy patients.  Proteinuria, specifically albuminuria, in CKD patients is associated with more rapid progression of disease and an increasing likelihood of developing end-stage renal disease.  Early detection of any proteinuria is essential for the treatment of this condition.  One major study has shown that screening for proteinuria is not cost-effective unless selectively directed at high risk groups which was defined as patients older than 60, and those with hypertension.

 

Most CKD patients should be considered for renal imaging studies as part of their initial evaluation.  The most common test is renal ultrasonography which is normally utilized to document the size of the kidneys.  With ultrasound, CKD usually manifests as small, echogenic kidneys, but occasionally, bilateral echogenic kidneys may be due to bilateral renal artery stenosis, so if that condition is suspected, CT or MR with associated angiography is recommended.  Rarely, hydronephrosis can cause renal insufficiency, so ultrasound can identify the rare cases of bilateral hydronephrosis (usually due to a pelvic tumor).  Occasionally, infiltrative processes can cause decreased renal function and ultrasound will identify large echogenic kidneys.  Lastly, autosomal dominant polycystic kidney disease (ADPCKD) may result in renal dysfunction and ultrasound is good at identifying the enlarged kidneys with multiple cysts.

 

Proper staging of CKD will facilitate application of clinical practice guidelines, clinical performance measures and quality improvement efforts to the evaluation and management of chronic kidney disease (see Table 1).  Management of the disease includes blood pressure control, glycemic control in diabetic patients and reduction of proteinuria with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin II receptor blocker (ARB).  Other interventions that may be beneficial include lipid lowering measures, especially with HMG CoA reductase inhibitors (statins), limiting dietary protein intake to 0.60 to 0.75 g/kg body weight in patients with a GFR below 25 mL/min/1.73 m2, and partial correction of anemia.  Regarding the use of ACE inhibitors and ARBs, there is growing evidence that higher doses of these medications are necessary to provide optimal reduction in proteinuria and that both of these agents provide similar renoprotective effects.

 

Table 1 – Stages of Chronic Kidney Disease

Stage

Description

GFR (mL/min/1.73m2)

1

Kidney Damage with normal or ↑ GFR

>90

2

Kidney Damage with mild ↓ GFR

60 - 89

3

Moderate ↓ GFR

30 - 59

4

Severe ↓ GFR

15 - 29

5

Kidney Failure

<15 (or dialysis)

 

Most patients with CKD do not die of kidney failure, but rather of CVD complications, which are often worsened by diabetic disease.  Studies have indicated that anemia, ↓GFR and microalbuminuria are associated with the CVD prevalence, and when all three are present, approximately 25% of the CKD patients had documented CVD.  Regarding the outcome of mortality, neither CKD nor diabetes had a hazard ratio as high as that of CVD in the study sponsored by the National Kidney Foundation.  Additionally, CKD is associated with increased morbidity and mortality in heart failure patients.  Accordingly, increased lipids need to be managed aggressively in patients with CKD.  The current CKD guidelines recommend an LDL cholesterol goal of less than 100 mg/dL.

 

A frequent question with CKD patients is when to refer to nephrology.  In the primary care setting, all patients should undergo evaluation with internal medicine or nephrology regarding the etiology of renal dysfunction.  Young patients (e.g., the active duty population) should be followed closely in an internal medicine or nephrology clinic since the preservation of remaining renal function is particularly important.  In general, patients with GFR <30 mL/min/1.73 m2 (CKD Stages 4–5) and those with >500mg/24 hr proteinuria should be referred to a nephrologist.

 

Aeromedical Concerns: Progressive kidney disease is not compatible with military aviation since the nature of the military mission may keep the aviator away from necessary medical care and speed the decline of the disease.  Documented decreased renal function in an applicant for military aviation service should not be waiverable as there is a reasonable chance the condition may progress.  In a trained aviator, stable decreases in renal function without systemic effect (such as electrolyte disturbances) may be acceptable for waiver.  A primary concern with this population is the risk of cardiovascular disease.  These folks need to be closely monitored on a regular basis with strict cardiac risk factor modification.

 

 

Medical Work-up: Waiver request for any aviator with chronic kidney disease should include a complete history of the problem to include all consultants seen as well as all physical exam results.  Labs need to include all urinalysis tests to include protein and albumin results, BUN/Cr, eGFR, 24 hour urine (if applicable), renal biopsy results if done.  If imaging tests were a part of the evaluation, those results are necessary.  The current treatment to include all medications and dates started is required as is a consultation from the treating nephrologist or internist.  Finally, details of all other medical problems are important.

 

Aeromedical Disposition:

 

Air Force: All forms of chronic kidney diseases are disqualifying for aviation duty in the Air Force.  The only medications considered for waiver are those on the approved medication list at the time of the waiver submission.

 

Army: Chronic kidney disease is disqualifying for aircrew and not waivered.  There are no APLs covering this disorder but once the diagnosis is made a permanent medical suspension is issued.

 

Navy:  A specific waiver policy for CKD has not been established.  Waivers are considered on a case-by-case basis.

 

Civilian: There are many airmen with chronic renal disease with all classes of medical certification.  Once renal failure occurs they are denied their medical.  The upper limit that the FAA will allow creatinine to go is somewhat loose but generally up around 2.5.  First- and second-class airmen are generally followed with yearly BUN, Creatinine, electrolytes, and CBC.  Third-class airmen without coronary disease are followed every other year while those with are checked yearly. 

 

Waiver Experience:

 

Air Force: AIMWTS review revealed five cases submitted for the diagnosis of chronic kidney disease.  There were 0 FCI/IA cases, 4 FC II cases and 1 FC III case.  All of the FCII cases were disqualified; two had gone on to kidney transplant, one had co-existent left ventricular hypertrophy and the other had several other medical problems.  The FC III case was a stable stage 2 case being treated with lisinopril and was given a waiver.

 

Army: Over a recent two year period there were 1,741 unique rated aircrew encounters filed in the Army Aeromedical Epidemiological Data Repository.  Among these there were no cases of chronic kidney disease.

 

Navy: Not available at this time

 

Civilian: Statistical data are not currently kept for airmen with this condition. 

 

ICD 9 code for Chronic Kidney Disease

585

Chronic Kidney Disease

 

References:

 

Coresh J, Selvin E, Stevens LA, et al.  Prevalence of Chronic Kidney Disease in the United States.  JAMA, 2007; 298:2038-47.

 

Levey AS, Coresh J, Balk E, et al.  National Kidney Foundation Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification, and Stratification.  Ann Intern Med, 2003; 139:137-47.

 

Snyder S and Pendergraph B.  Detection and Evaluation of Chronic Kidney Disease.  Am Fam Physician, 2005; 72:1723-32.

 

Go AS, Chertow GM, Fan D, et al.  Chronic Kidney Disease and the Risks of Death, Cardiovascular Events, and Hospitalization.  N Eng J Med, 2004; 351:1296-1305.

 

Ryan TP, Sloand JA, Winters PC, and Corsetti JP.  Chronic Kidney Disease Prevalence and Rate of Diagnosis.  Am J Med, 2007; 120:981-86.

 

Levey AS and Coresh J.  Clinical Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification, and Stratification.  National Kidney Foundation, 2002.

 

Post TW and Rose BD.  Diagnostic approach to the patient with acute or chronic kidney disease.  UpToDate.  Online version 17.2 May 2009.

 

Wilhelm-Leen ER, Hall YN, Tamura MK, and Chertow GM.  Frailty and Chronic Kidney Disease: The Third National Health and Nutrition Evaluation Survey.  Am J Med, 2009; 122:664-71.

 

Rule AD, Larson TS, Bergstralh EJ, et al.  Using Serum Creatinine to Estimate Glomerular Filtration Rate: Accuracy in Good Health and in Chronic Kidney Disease.  Ann Intern Med, 2004; 141:929-37.

 

1Boulware LE, Jaar BG, Tarver-Carr ME, et al.  Screening for Proteinuria in US Adults: A Cost-effectiveness Analysis.  JAMA, 2003; 290:3101-14.

 

Lisanti C.  Personal communication with Dr. Lisanti, retired AF radiologist, working at Brooke Army Medical Center.

 

Ripley E.  Complementary effects of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in slowing the progression of chronic kidney disease.  Am Heart J, 2009; 157:S7-S16.

 

McCullough PA, Jurkovitz CT, Pergola PE, et al.  Independent Components of Chronic Kidney Disease as a Cardiovascular Risk State.  Arch Intern Med, 2007; 167:1122-29.

 

Ahmed A and Campbell RC.  Epidemiology of Chronic Kidney Disease in Heart Failure.  Heart Failure Clin, 2008; 4:387-99.

 

 

2/23/11

Prepared by Dr. Dan Van Syoc