Nutrition and Renal Disease

Diet plays a significant role in management of patients with a variety of renal diseases.
 

Here are two quick examples, which we will revisit later.

1)       A patient with mild renal insufficiency who also has HTN needs to be on a Na restricted diet because there is a close relationship between Na intake and BP

2)       A patient with nephritic syndrome loses protein in urine and should be on a protein-restricted diet.  This is especially true in patients with diabetes (both type 1 and 2) because high protein diet promotes the progression of kidney disease. 

By the end of this lecture we should be able to:

1)       Understand goals of nutritional therapy in renal patients

2)       Evaluate contributing factors for malnutrition

3)       Learn how to assess the nutritional status

4)       Assess requirements for:

a.        Energy

b.        Protein

c.        Electrolytes

d.        Vitamins

e.        Trace elements

f.         Fluid status
 

Terminology (focus on ESRD!)

• Normal values
  • Serum creatinine: 0.8 – 1.4 mg/dL AND
  • Glomerular Filtration Rate or creatinine clearance: 100 ml/min
• Chronic Renal Failure
  • Serum creatinine: >1.5 mg/dL OR
  • Glomerular Filtration Rate: < 100 ml/min
• **End Stage Renal Disease**
  • Glomerular Filtration Rate: < 15 ml/min
  • Patients will definitely be symptomatic with that low of a Glomerular Filtration Rate and need dialysis

• Dialysis
  • Treatment modality to remove nitrogenous waste (accum of urea nitrogen, etc).
  • Also called “artificial kidney”
• Acute Renal Failure
  • Acute deterioration in renal function OR
  • Sudden increase in creatinine levels >1.5 mg/dL
• Nephrotic Syndrome
  • Urinary protein >3.5 g/day
  • Edema
  • Hypoalbuminemia
  • Hyperlipidemia
  • Lipiduria

   

Goals of Nutritional Therapy (especially for renal patients)

1)       Maintain good nutritional status (ie maintain body protein stores) in order to maintain good quality of life for the pts

2)       Prevent symptoms of renal failure (such as nausea, vomiting, loss of appetite, weight loss, etc)

3)       Most importantly if you are a good nephrologist: Prevent further deterioration of renal function (ie prevent increase in serum creatinine) to delay progression to ESRD. 

We’ll start with a case here and then come back to it in the end:

            25 y/o man had DM 1 for 18 years and progressive renal failure with proteinuria (3.7 g/d) {AKA nephrotic syndrome}.  He presents for an initial office visit in which you instruct him to follow a low protein diet of 0.6 g/kg/day with 30 of those grams coming from high biologic value protein.  He weighs 66kg.  His initial creatinine is 3.0 mg/dL

He returns 2 mos later:

• Serum creat: 4.1 mg/dL
• 24-h urine volume: 2.5 L
• Urine urea nitrogen: 3 g/L
• Urine creatinine: 60 mg/dL
• 24-h protein: 4.8 g/d – most important finding because increase significantly from 2 mos ago (3.7 g/d).  This is terrible for pt and for physician

What’s the proper course of action ?? … stay tuned! (or read the last page)

Factors Contributing to Malnutrition

• Poor dietary intake especially due to edema from nephrotic syndrome:
  • edema = appetite loss/nausea = more edema AND/OR
  • edema in gut = impaired absorption
• Abnormal muscle metabolism – catabolic state in which muscle is breaking down
• Abnormal nutrient metabolism
• Uremic toxins – metabolites of protein catabolism are retained
  • The Uremic Society describes over 200 uremic toxins retained in RF patients
• Loss of nutrients to dialysate – very common so dialysis patients need supplements
• Blood loss in hemodialysis
• Dialysis catabolism – dialysis puts pts in catabolic state
• Intercurrent illnesses and Infections
  • Dialysis patients for some reason have ongoing inflam shown by chronically increased CRP which can lead to intercurrent illnesses and infections

Assessment of Nutritional Status (in dialysis units or clinics)

1)       Anthropometry (didn’t talk about them)

a.       Height

b.       Weight

c.       Skin-fold thickness (triceps, subscapular)

d.       Midarm circumference

2)       Biochemical Markers ** - we pay more attention to these as clinicians**

a.       Total protein

b.       Albumin –

                                                               i.      Most extensively examined because albumin levels correlate with mortality in dialysis pts

                                                             ii.      There are two problems with serum albumin though: first, it has a long half life (2-3 weeks) and second, it has a high distribution in various compartments

                                                            iii.      But it’s still the best one to measure for now

c.       Transferrin – follow in dialysis pts every month

d.       Prealbumin – helps in transfer of peroxin and is good marker of nutritional status in dialysis and CRF pts; but has many problems so don’t routinely follow this

These last four are time consuming and not routinely followed:

3)       Plasma amino acid concentration – usually essential AA decr and non-essential incr

4)       Whole body protein turnover

5)       Nitrogen balance

6)       Assessment of protein intake

____________

• Why do we follow serum albumin? 
• Because it has been studied most and we’ve assoc albumin and mortality
• Low albumin levels are associated with high mortality level in dialysis patients
• A neat little graph showed us that when serum albumin < 2.5g/dL, the risk of mortality increase 20X compared with patients in normal range 4.0-4.5 g/dL
• Due to this study and other similar ones, federal government has insisted us to use albumin as marker to determine mortality
• You must maintain at least 3.5 g/dL albumin
• As an aside, we were told about a female patient who weighed only 46 lbs due to RF.  They began dialysis and nutritional supplements and she gained about 40 lbs.  Sounds like a miracle story?  Not quite, she died due to intercurrent illnesses shortly there after. 

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