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High-resolution manometry is the gateway physiologic test after a clean endoscopy in esophageal dysphagia or pre-fundoplication evaluation. The Chicago Classification version 4.0 reduces the report to four numbers read in a fixed hierarchy: relaxation first, propagation second. Once you hold that order, every diagnosis falls out. This episode walks the framework and applies it to achalasia, where elevated IRP plus body pressurization pattern picks the subtype and the therapy.
The case. A patient with progressive solids-and-liquids dysphagia. Manometry reports an IRP of 22, a DCI of 300, and a distal latency of 4.0 seconds. Which achalasia subtype, and which definitive therapy?
Topics covered
Key decisions
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Board Pearls is a gastroenterology board review built around clinical reasoning, not recall. Each episode takes one high-yield topic and works it the way you would on rounds: a case to anchor it, the framework that sorts the differential, and the specific decisions the exam rewards.
The gastroenterology series covers the full blueprint across nine modules: esophagus, stomach and duodenum, small bowel, colon, pelvic floor, liver, pancreas and biliary, endoscopy, and the cross-cutting topics. Episodes are grouped by chapter and built from the primary guidelines and pivotal trials the boards draw from (ACG, AGA, AASLD, ASGE), not from textbook summaries.
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Welcome to Board Pearls. This is episode one of two of the Esophageal Motility chapter, in the Esophageal Disorders module. In this episode we cover manometry first principles and achalasia: the Chicago version four hierarchy that puts EGJ outflow first and peristalsis second, and the three achalasia subtypes that each map to a specific therapy.
Start with the single mechanical fact that organizes everything else. The esophagus has two jobs on every swallow. The lower esophageal sphincter has to relax so the bolus can pass. The smooth muscle body has to contract in a sequential, time-locked wave that pushes the bolus distally. High-resolution manometry measures both jobs at thirty-six pressure points from the upper sphincter to the stomach. The Chicago Classification version four reads those measurements in a fixed order. It checks outflow first because outflow obstruction is the highest-stakes diagnosis. It checks peristalsis second because the answer there depends on whether the wave is missing, premature, hypercontractile, or fragmented. Every parameter the candidate needs is a measurement of one of those two jobs, and every diagnosis falls out of the hierarchy.
The catheter sits across the esophagus and the software displays the pressures as a color topography plot called a Clouse plot. Axial position is on the vertical axis. Time is on the horizontal. Pressure is encoded by color. The standardized protocol for version four is ten five-milliliter water swallows in the supine position, then five swallows in the upright position. Multiple rapid swallows probe contraction reserve. A rapid drink challenge of two hundred milliliters through a straw provokes pressurization when EGJ outflow obstruction is suspected. The protocol matters because version four grades several diagnoses on position-dependent thresholds. A study without upright swallows cannot finish the algorithm.
The integrated relaxation pressure is the gate, and it is worth understanding what it actually measures before reaching for the number. It is the lowest mean pressure across the esophagogastric junction during any four non-contiguous seconds of the ten-second window that opens at the start of the swallow. The software follows the sphincter as it moves with respiration, which is what the electronic sleeve sensor approximates. So the IRP is not the resting LES tone. It is a measurement of how completely the sphincter lets go when it is supposed to. On the Medtronic system, supine IRP under fifteen is normal and upright IRP under twelve is normal. The split between supine and upright matters because the IRP is the gate that splits the algorithm. An elevated IRP routes the case into the EGJ outflow group. A normal IRP routes it into the peristaltic group. The algorithm never asks about peristalsis until the IRP question is answered.
The distal contractile integral is the next parameter and it measures contractile vigor in the smooth muscle segment of the esophagus, which is the distal two-thirds. The DCI is the volume of the three-dimensional pressure topography mountain in that segment. It is pressure times length times duration. The thresholds carve the peristaltic spectrum into categories. Under one hundred is failed. One hundred to four hundred fifty is weak. Four hundred fifty to eight thousand is normal. Over eight thousand is hypercontractile. A DCI of zero on a single swallow means the swallow produced no smooth muscle contraction at all. One hundred percent failed peristalsis across the ten swallows is a load-bearing finding. If the IRP is normal, it defines absent contractility. If the IRP is elevated, it defines achalasia, and the subtype is then a question of what else the body does on those failed swallows.
The distal latency is the third parameter and it measures premature contraction. It is the time from upper sphincter relaxation at the start of the swallow to the contractile deceleration point near the EGJ. Normal is four-and-a-half seconds or longer. Under four-and-a-half seconds the contraction has reached the distal esophagus too early relative to swallow initiation. That is the manometric definition of a spastic contraction. The short distal latency turned out to be a more specific marker for spasm than the older parameter of contraction front velocity, and contraction front velocity has been removed from the version four algorithm entirely.
Contraction pattern captures fragmentation. A peristaltic break of more than five centimeters in the twenty-millimeter isobaric contour with a DCI above four hundred fifty is a fragmented swallow. Seventy percent or more ineffective swallows, or fifty percent or more failed swallows, defines ineffective esophageal motility when the IRP is normal. The version four definition is more stringent than the prior one and now includes fragmentation, which is why the IEM diagnosis rate dropped meaningfully when the new criteria were adopted.
The hierarchy is what carries the algorithm. Step one is the IRP. If the IRP is elevated and there is no peristalsis on any swallow, the diagnosis is achalasia, and the subtype follows from the pressurization and spasm pattern. If the IRP is elevated and some preserved peristalsis remains, the diagnosis bucket is EGJ outflow obstruction. Version four now requires confirmation in both supine and upright position. It requires intrabolus pressurization on at least twenty percent of swallows. It requires symptoms and a confirmatory test. If the IRP is normal, the algorithm shifts to peristalsis. One hundred percent failed is absent contractility. Premature contraction with short distal latency in twenty percent or more of swallows, plus symptoms, is distal esophageal spasm. DCI over eight thousand in twenty percent or more of swallows, plus symptoms, is hypercontractile esophagus. The seventy and fifty percent thresholds define IEM. The symptom requirement for spasm and hypercontractile esophagus is new in version four, and the reason is that asymptomatic short-latency or high-DCI swallows are common in healthy people and are not a disease.
A few adjunctive maneuvers fill in gaps in the standard ten-swallow protocol. Multiple rapid swallows probe the latent contractile reserve of the smooth muscle. Five small wet swallows two to three seconds apart should produce a single robust contraction after the last swallow that exceeds the mean DCI of the standard swallows. Absence of this contraction reserve in a patient with IEM predicts dysphagia after fundoplication and is the data point that argues against a wrap. The rapid drink challenge with two hundred milliliters of water through a straw is used to provoke EGJ outflow obstruction when standard swallows are equivocal. FLIP topography rescues studies in which the IRP is borderline or in which the manometric pattern conflicts with the clinical impression, and the FLIP framework is the subject of the next episode.
Opioids deserve their own paragraph here because they confound every part of the algorithm. Chronic opioids elevate the IRP by impairing sphincter relaxation. They raise the DCI by inducing hypercontraction. They shorten the distal latency by inducing premature contraction. The combination produces a manometric phenotype that mimics type three achalasia, EGJ outflow obstruction, distal esophageal spasm, or hypercontractile esophagus depending on which parameter dominates. When a patient on chronic oxycodone or methadone or buprenorphine shows up with one of these patterns, opioid withdrawal is the first therapeutic test. Committing a chronic pain patient to a myotomy on a manometric tracing that the opioid produced is the failure mode the question stems are built to catch.
Now to achalasia, because the version four hierarchy lands here often enough that the subtypes deserve attention on their mechanism before their treatment. The pathologic lesion is degeneration of the inhibitory neurons of the myenteric plexus, the nitric-oxide-producing ganglion cells that normally trigger sphincter relaxation and propagate the sequential wave. The cholinergic excitatory neurons that maintain sphincter tone are relatively spared. So the resting LES pressure is often elevated, and the sphincter cannot let go in response to the swallow. The smooth muscle of the body loses the spatial gradient that normally generates a propagated contraction. The body then either falls silent, pressurizes uniformly along its full length when the bolus has nowhere to go, or generates premature spastic contractions in the distal segment. Those three behaviors are the three subtypes, and every other thing that matters about achalasia follows from them.
The presentation is insidious. The dominant symptom is dysphagia to both solids and liquids from the start, because a failed propagated wave fails on every consistency. Patients describe food piling up in the chest. They drink large volumes of water with meals to push the bolus through. They stretch the neck and stand upright after meals. They reach for carbonated beverages because the carbonation provides a column of pressure that overcomes the sphincter. Regurgitation of undigested food is common. Nocturnal regurgitation that leaves food on the pillow is a high-yield clue because it tells you the esophagus is dilated and stagnant. Heartburn is reported in over forty percent of patients despite the absence of acid reflux, and the mechanism is fermentation of retained food and esophageal stretch rather than acid contact. Weight loss in primary achalasia is typically minimal, and that is the feature that separates it from pseudoachalasia.
Diagnosis begins with EGD because primary achalasia is a clinical diagnosis of exclusion and pseudoachalasia has to be ruled out. The endoscopist sees a dilated esophagus that often contains residual food and saliva. The mucosa looks normal. The EGJ is tight but opens with gentle pressure on the scope, which is distinct from the firm resistance of an obstructing tumor. EGD is normal in up to forty percent of achalasia, so a normal endoscopy does not exclude the diagnosis. Barium esophagram shows a dilated esophagus tapering to a smooth bird-beak narrowing at the EGJ, with retained barium and absent peristaltic stripping. Plain chest radiograph in advanced disease shows mediastinal widening and absence of the gastric air bubble because air cannot enter the stomach across the unrelaxing sphincter. High-resolution manometry confirms the diagnosis and assigns the subtype.
Type one is the silent body. The IRP is elevated, every swallow is failed, and there is no panesophageal pressurization. The smooth muscle has lost the tone that would generate even passive pressurization, which is why type one tends to occur in older or more advanced disease where the esophagus has dilated and decompensated. Treatment response across modalities is intermediate. The Pandolfino series reported around fifty-six percent success at the last intervention for type one.
Type two is the pressurizing body. The IRP is elevated, every swallow is failed, and twenty percent or more of swallows show panesophageal pressurization. Panesophageal pressurization is defined as a simultaneous pressure rise of more than thirty millimeters of mercury that spans the full length of the esophagus. The mechanism is that the smooth muscle still has tone but cannot generate a propagated wave. The bolus has nowhere to go, so the column of fluid pressurizes uniformly between a closed sphincter and a tonically active body. Type two is the best responder to every modality, because the muscle that produces the pressurization is still alive and the body has not yet decompensated. The same Pandolfino series reported around ninety-six percent success at the last intervention for type two. That number is the reason a stem with panesophageal pressurization on every swallow is asking the candidate to recognize the best-prognosis subtype.
Type three is the spastic body. The IRP is elevated, and twenty percent or more of swallows show premature contractions with a short distal latency and a DCI above four hundred fifty. The mechanism couples failed sphincter relaxation with hyperexcitable smooth muscle in the distal segment. The chest pain that bothers these patients reflects those spastic contractions. The Pandolfino series reported essentially no success for type three with pneumatic dilation, and that data point is what removes dilation from the menu for this subtype. The reason is mechanical. The spastic segment extends well above the LES, and a balloon at the LES does not address the segment above it. A longer tailored myotomy does, and POEM allows the operator to set the proximal extent of the myotomy under direct vision. That is why POEM is the preferred operation for type three.
Now to the therapies themselves, with the principle that organizes them stated first. No therapy restores peristalsis. Every therapy aims to lower the LES pressure so that gravity and intra-esophageal pressure push the bolus through. Every intervention loses efficacy over time. Patients should be counseled at the start that achalasia is a chronic disease, that roughly one in three will need additional intervention at some point, and that the choice is among imperfect options.
Medical therapy with calcium channel blockers and nitrates taken sublingually before meals offers limited and short-lived relief. Side effects and tachyphylaxis limit chronic use. Medical therapy is reserved for patients who cannot tolerate definitive procedures and who have failed botulinum toxin.
Botulinum toxin injection at the LES, eighty to one hundred units divided into four quadrants, poisons the cholinergic excitatory neurons and decreases sphincter pressure for a median of about six months. Repeat injection gives diminishing returns. Botulinum toxin is reserved for elderly or infirm patients in whom dilation or myotomy poses unacceptable risk. There is a cost beyond the short half-life. Botulinum injection creates submucosal scarring at the LES, which raises the perforation rate at the time of a subsequent surgical myotomy from around seven percent to over fifty percent in some series. So the choice is consequential. Injecting a thirty-five-year-old who could have had a Heller closes off a clean operative plane for the future.
Pneumatic dilation uses progressively sized thirty to forty millimeter balloons to tear the LES muscle fibers. Single-session response is sixty to eighty-five percent in the short term, but roughly half of patients require additional therapy within five years. Perforation occurs in two to five percent. Reflux esophagitis develops in around five percent. Pneumatic dilation is contraindicated in type three because the spastic body extends above the LES and the dilation does not address the spastic segment. Dilation in type three is the wrong answer on the boards.
Laparoscopic Heller myotomy with partial fundoplication cuts the muscle fibers of the LES under direct surgical exposure and adds a partial wrap to mitigate the post-operative reflux that follows. The wrap is either a Dor anterior wrap of one hundred eighty degrees or a Toupet posterior wrap of two hundred seventy degrees. Nissen is avoided because the body has no peristalsis to push past a full wrap. A complete wrap on a paralyzed esophagus converts the patient from dysphagia of failed motility into dysphagia of mechanical obstruction. Heller provides good to excellent symptom relief in seventy to ninety percent at one year. Reflux esophagitis develops in roughly ten percent. The European randomized trial of pneumatic dilation versus laparoscopic Heller with Dor showed essentially equivalent success rates at one, two, and five years, with no difference in reflux outcomes.
Per-oral endoscopic myotomy is performed in three moves. The operator creates a submucosal tunnel in the esophagus. The inner circular muscle of the lower esophagus and LES is cut through the tunnel with a diathermic knife. The mucosal entry is then closed with clips. The key feature that distinguishes POEM from Heller is that the operator can tailor the proximal extent of the myotomy. That is why POEM is the preferred operation for type three, where a longer myotomy is needed to address the spastic segment. POEM is not routinely combined with an antireflux procedure, and post-POEM reflux is the principal trade-off. Abnormal acid exposure on pH testing is found in around forty-seven percent after POEM and reflux esophagitis in forty to forty-four percent in randomized trials, compared with single-digit to roughly thirty percent after Heller. Two randomized trials anchor the numbers worth carrying. The first, POEM versus pneumatic dilation, showed POEM success of ninety-two percent at two years and eighty-one percent at five years versus fifty-four and forty percent for dilation. The second, POEM versus laparoscopic Heller with Dor, showed essentially equivalent clinical success at two and five years, with the expected post-POEM reflux penalty.
Blown-out myotomy is a complication unique to surgical myotomy and POEM. It is defined as a fifty percent increase in distal esophageal diameter at the myotomy site. It develops in roughly thirty percent of patients within five years of POEM and is associated with treatment failure, higher acid exposure, and recurrent regurgitation. Blown-out myotomy occurs most commonly after type three treatment because the residual spastic contractions blow out the weakened myotomy site.
So the consensus that the boards reach for is this. Pneumatic dilation, Heller with partial fundoplication, and POEM are comparably effective for type one and type two, and the choice among them depends on local expertise, patient preference, reflux tolerance, and durability preference. POEM is the preferred operation for type three. Botulinum toxin is reserved for non-candidates for definitive therapy, with the caveat that it complicates a future Heller. The randomized trials show the dilation-versus-Heller equivalence, the POEM-versus-dilation superiority of POEM at two and five years, and the POEM-versus-Heller equivalence with the reflux trade-off.
One vignette is worth setting up here because it is the one mechanical application of the algorithm gets wrong. An older patient, sixty-five or older, presents with dysphagia of four to six months and disproportionate weight loss. The manometry meets criteria for achalasia. The temptation is to call this primary achalasia and route the patient to dilation or POEM. The temptation is wrong. Up to five percent of patients meeting manometric criteria for achalasia have pseudoachalasia. In pseudoachalasia an infiltrating cancer at the EGJ produces an achalasia-like phenotype. It does so by direct invasion of the myenteric plexus, by mechanical narrowing, or by paraneoplastic immune-mediated injury. Small cell lung cancer is the canonical paraneoplastic cause, with circulating anti-neuronal antibodies. The malignant cause is often missed at standard EGD because the tumor infiltrates the muscularis without producing a mucosal lesion. The three clues are age over sixty, symptom duration under six to twelve months, and weight loss out of proportion to the symptom burden. The right next move is endoscopic ultrasound to look for a submucosal or extrinsic mass at the EGJ, and cross-sectional imaging to look for thoracic, pulmonary, or upper abdominal malignancy. The candidate who runs to a myotomy on this stem missed the point.
Chagas disease is the secondary cause worth recognizing on history. Trypanosoma cruzi destroys the same ganglion cells that primary achalasia destroys, and a patient who emigrated from rural Latin America with a megacolon and a dilated bird-beak esophagus has the clinical syndrome. Serology and PCR confirm. Treatment is the same therapeutic options as for primary achalasia, addressed to the same end organ.
So the synthesis is this. High-resolution manometry under Chicago version four reads two jobs in order. It checks whether the sphincter relaxes, by the IRP. It checks whether the body contracts in the right pattern, by the DCI, the distal latency, and the contraction pattern. An elevated IRP with no peristalsis is achalasia, and the subtype is determined by what else the body does on those failed swallows. A silent body is type one. A pressurizing body is type two. A spastic body is type three. The subtype maps to the therapy because the muscle that does or does not work changes what the procedure has to accomplish. Type one and type two get pneumatic dilation, Heller, or POEM with the choice driven by local expertise and reflux trade-offs. Type three gets POEM because the longer tailored myotomy is the only intervention that reaches the spastic segment, and pneumatic dilation is wrong. The whole framework collapses in two patients. The first is the patient on chronic opioids, in whom the mimic pattern resolves with opioid cessation. The second is the older patient with a short symptom history and disproportionate weight loss, in whom pseudoachalasia has to be ruled out before any procedural therapy.
In the next episode we move to the rest of the version four map. That set is the disorders on the other side of the IRP gate. Distal esophageal spasm and jackhammer esophagus, where the IRP is normal and the body is hyperexcitable. Scleroderma and absent contractility, where the dual hit of failed peristalsis plus a hypotensive LES drives severe reflux rather than dysphagia. And EGJ outflow obstruction, the heterogeneous bucket that version four now requires symptoms and a confirmatory test of FLIP or timed barium before treating, because the manometric finding alone is too non-specific to act on.