BACKGROUND: Achalasia is defined manometrically by an aperistaltic esophagus. 
Variations in the manometric findings occur in achalasia suggesting that all 
manometric features should not be required to diagnose achalasia. Combined 
multichannel intraluminal impedance and esophageal manometry (MII-EM) allows 
both a functional and a manometric evaluation of esophageal motility and 
identifies chronic fluid retention.
AIM: To compare manometric and MII characteristics in patients with achalasia.
METHODS: Retrospective review of 73 MII-EM tracings from patients with achalasia 
done in our laboratory between October 2001 and December 2004 (38 females; mean 
age=53.5 y). Patients with previous esophageal interventions were excluded. 
Manometric and MII characteristics were identified and compared during 10 liquid 
and 10 viscous swallows. Patients were also divided into 2 groups: vigorous 
achalasia (VA) and achalasia.
RESULTS: Twenty-two of the seventy-one (31%) achalasia patients had a 
hypertensive lower esophageal sphincter (LES). The mean lower esophageal 
sphincter pressure (LESP) for the 71 patients with achalasia was 37.9+/-21.2 mm 
Hg compared with 27.3+/-9.3 mm Hg (P<0.05) in the 73 patients with normal 
motility. The mean LESP in patients with achalasia was 36+/-20.3 mm Hg compared 
with 47+/-23.2 mm Hg (P<0.05) in patients with VA. Elevated intraesophageal 
pressure (IEP) was noted in 45/73 (61.6%). The mean LESP in this group was 
41.1+/-22.9 mm Hg compared with 32.5+/-17 mm Hg (P<0.05) with normal IEP. The 
mean baseline impedance for achalasia was 801+/-732 compared with 1265.2+/-829.5 
Omega (P<0.05) for the VA patients.
CONCLUSIONS: Most patients with achalasia have elevated IEP, elevated LES 
residual pressure, normal LES pressure, and low baseline impedance. All 
manometric features should not be required to diagnose achalasia. Patients with 
an elevated IEP are likely to have an elevated LES pressure and LES residual 
pressure. Low MII values identify chronic fluid retention and helps confirm the 
diagnosis.